ButDoISay

A Science Guy's Life on the Medtronic MiniMed 670G Insulin Pump and More.

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Use Tegaderm Film in place of the Medtronic Oval Tape for the Guardian 3 or Enlite CGM Systems

Tegaderm Film to the Rescue

When I run out of the oval tape that comes with the Guardian 3 Sensors for the MiniMed 670G, the Tegaderm Film by 3M comes in very handy. I used these films for my Enlite sensor and the Medtronic MiniMd 530G.

The oval tape is a little complicated for me that I end up peeling the wrong side or get it all tangled up before applying it on my skin.

It seems as if I end up using an extra one during insertion and running out of the oval tape the tail end of my 3 moth supply.

Tagaderm Film by 3M purchased on Amazon

The Tegaderm Film comes in different sizes and works well in covering the sensor and making it water proof just like the oval tape.

This summer I tested out two sizes bought at Amazon.

The larger size Tagaderm film (4”x43/4”)worked well for when I had to jump into the pool with the kids but it covers such a large area.

I liked the assurance that the sensor was completely waterproofed over a large area.

With the larger Tegaderm Film you certainly do not need apply extra tape under the Transmitter.

The smaller sized Tegaderm Film (2.375”x2.75) fits the same as the oval tape.

The only downside to the Tegaderm Film is that it will peel off if you do not apply it firmly to your skin.

The films can be pricey at local Pharmacies but you should get very reasonable prices (no more than $.50 per tape) on Amazon or Ebay.

Dawn Phenomenon and Auto Mode

According to Medtronic, Auto Mode does not learn an individual’s time of day patterns or diurnal variations (i.e., dawn phenomenon) for the Medtronic MiniMed 670G.

Medtronic recommends the following for dawn phenomenon (word-for-word):

Morning highs: Assess for overnight / bedtime highs first, bedtime snack with inadequate or no bolus, morning caffeine. If issue is identified as dawn phenomenon, have patient test BG, take recommended correction dose and bolus for breakfast at least 15-20 minutes before eating. “

SEe this medTronic document

The same would most likely apply for the Somogyi effect.

Basically for both the Somogyi effect and dawn phenomenon, your fasting BG reading are elevated in the morning due to peak production of the cortisol hormone (dawn phenomenon) or your live compensating for low sugar at night (somogyi effect)

Read more on dawn phenomenon and the Somogyi effect and strategies for dealing with both at integrateddiabetes.com

Finding success with Auto Mode for the Medtronic MiniMed 670G

Since Auto Mode is adaptive and conservative in nature, patience must be exercised and expectations curtailed to reasonable levels.

I can say it took me about a year to get to the point where I was comfortable with Auto Mode. And if you are hoping for a HbA1c of 5.7 with Auto Mode, it will not happen unless you are following a very compliant diet.

Realistically I would say that a HbA1c between 6.5 and 7.0 is easily achievable with Auto Mode without changing your pre-Auto Mode diet or habits. 

But here are some tips from my experience on how to be successful in using Auto Mode to achieve the realistic HbA1c goals discussed above.

Get the new Enhanced Guardian 3 Transmitter (Version 2.2)

A lot of frustration for many users with Auto Mode arose from the defective first generation sensor transmitter that made it hard to enter Auto Mode due to the infamous “BG required loop”.

Medtronic resolved this issue with their new enhanced transmitter. I must say that I have had a lot of success with this new transmitter.

Using the upper thigh as a sensor insertion site, the guardian sensor is very accurate and in my view comparable to the Dexcom 5 which I used prior to getting the 670G. The new transmitter makes the CGM sensor experience even more pleasant.

The enhanced transmitter is a good foundation to finding success with Auto Mode since the more accurate the sensor, the better the control. The less the number of incessant errors and alarms at night, the higher the chance you will stick it out with Auto Mode.

To request for the new enhanced transmitter follow the link below:

https://info.medtronicdiabetes.com/122018_US_DIB_Patient_BG-670G-Request-Form?

I received the following message when my Diabetes educator ordered my enhanced transmitter.

Know your carb ratio(s) and master your carb counting

Knowing your carb ratio is very important since this is one of the two inputs that Auto Mode uses to keep your readings close to the Medtronic advertised BG target of 120 mg/dL.

Just remember, with Auto Mode, you will have to dial you manual mode carb ratio by about 1-2 points. So if your carb ratio is around 10 when you are in manual mode, it is likely that your effective carb ratio for Auto Mode will be somewhere between 8 and 9.

Having carb ratios really off will result in the pump becoming overly aggressive or really conservative. Over bolusing causes the pump to cut back on basal and micro bolus. For me if I go for long without the basal or microbolus, I feel fatigued and have to always deal with a spike if I end up eating during these periods.

Under bolusing will obviously lead to highs that will make it hard for Auto Mode to stay on-track.

Periods of no basal or microbolus with the Medtronic Minimed 670G Auto Mode
Balance between Bolus and Basal – Periods of no basal or microbolus with the Medtronic Minimed 670G Auto Mode is marked by a lack of small purple dots on the sensor readout (dots signify basal/microbolus delivery).

Know that Auto Mode still requires discipline

Auto Mode does give you a little flexibility when it comes to your diet but it does not give you total freedom to do things you never did while in manual mode. For example, Auto Mode seems to get thrown off by constant snacking and bolusing. Constant bolusing really throws off basal delivery since the pump has to play a balancing act between basal and bolus to keep you within the 120 mg/dL target.

Similarly, Auto Mode requires mastery when it comes to eating foods with a high glycemic index or fatty food like pizza. It gets better with time but I normally exit Auto Mode and do dual bolusing when I eat such foods.

Do not try to trick Auto Mode

It is temping to give yourself a dose of bolus to correct high sugars under the guise of carb intake. Entering “fake or phantom carbs” really throws off Auto Mode.

Since Auto Mode assumes you ate with the bolus, it will continue to work hard to correct high sugars. What results is an accumulation of insulin that will cause your BGs to drop on the tail end of the insulin active time.

I have had scary lows at night as a result of trying to correct the high BGs right before bedtime outside Auto Mode’s recommended bolus.

Furthermore, the more Auto Mode keeps getting thrown off due to “fake carbs,” the more trouble you will have spiking and controlling hypoglycemic events.

If I must correct high sugars outside the recommended dose that Auto Mode suggests, I now exit to manual mode. Or else I just let Auto Mode take its time to getting me back on track.

Wait for 15-30 minutes to eat after Bolusing

I personally find waiting between 20-30 minutes helps with my post-meal spike control while in Auto Mode. The wait time is dependent on my pre-meal BG readings (longer times for higher BGs).

Auto Mode is not very good with Spike control as compared to manual mode and this can be a little frustrating. In manual mode, my basals and carb ratio are dialed down to a point where I have minimal spiking between meals.

Keep your Manual Basal up to date

It is important to make sure your basal patterns is still working well just in-case you have to exit from Auto Mode for a prolonged period of time due to illness or personal preference.

I am now making it a habit of exiting Auto Mode for two weeks every three months to optimize my basal patterns. This also seems to help my Auto Mode numbers.

This document by Medtronic for healthcare providers is the most detailed document I have read so far on Auto Mode and how to deal with different control scenarios.

Have a good Endocrinologist

Auto Mode and closed loop technology give us a glimpse of how complicated insulin pump therapy will become in the future. A good endocrinologist will keep up with the technology and help you fine tune your pump based on the training they continually receive from Medtronic or any other pump manufacturer.

As much as I hate going in to see my endocrinologist every three months, it has helped me achieve success with Auto Mode since it allows us to set  short-term strategies that can be evaluated during very visit.

BG Required Loop Issue now Resolved with New Enhanced Guardian 3 Transmitter

It has now been over three months since I received the enhanced Guardian transmitter to replace my first generation transmitter.

If you still have the first generation transmitter and are still fighting with the BG required loop issue contact your Medtronic educator to get the enhanced transmitter as soon as you can. It will save you a lot of grief.

Enhanced Transmitter Version for the Guardian 3 Sensor
The Enhanced Transmitter Version Number (Version 2.2) can be found under Status ->Sensor at the bottom.  

My initial thinking was that the Guardian 3 sensor transmitter was just a simple analog device that simply collected and sent analog data to the pump for post-processing conversion to digital data (data you see on your pump screen).

But I think there’s more to the transmitter, I think the circuitry is more complex and some of the calculations can be performed at the transmitter. This is great since that means Medtronic did not have to recall the pump to physically perform a hardware update to resolve this particular issue.

With the enhanced transmitter, the BG required loop that prevented one from entering Auto Mode is now completely resolved.

It also seems that the enhanced transmitter also handles data calibration differently and better.

The Medtronic 670G sensor calibration algorithm seems to behave very similarly now to the Calibration algorithm of the Dexcom 5 I used a couple years ago .

For example, the sensor readings seem to be averaged if the numbers between the sensor and the meter are not so close but not so varied.

In addition, if the number from the meter is so different from that of the sensor, the sensor will more readily default to the meter number more than before.

To request for the new enhanced transmitter follow this link.

I received the following message when my Diabetes educator ordered my enhanced transmitter.



 

A year Later – Success with Auto Mode

Exactly a year ago on this day, I met with my diabetes educator for my Medtronic MiniMed 670G training. Two weeks later I started using Auto Mode.

Along the way, I started documenting my journey on ButDoISay, nearly gave up on Auto Mode and certainly drove my endocrinologist crazy by constantly changing my delivery settings.

Her very words during our last appointment were: “Why change something if it ain’t broken”

Since we have a good rapport my answer was “You know, the scientist in me pushes me to fiddle with the settings. Right?!” And she just laughed.

Finally 100%. I took a year but I think am getting there
Time in Range is 91% in the last 7 days

Fittingly, yesterday for the first time I was 100% in Auto Mode and 100% in Target Range. Woohoo! I just can’t believe how the algorithm has learned my sugar basal rhythms in the last one year.

But seriously, the last year was also a very stressful year for me. Our youngest daughter was diagnosed with Autism at the start of 2018 and my life was completely changed. All of a sudden I started noticing all the missed milestones and my schedule was now filled with Autism parent training, speech therapy, and occupational therapy appointments.

However, the most stressful thing for me was not being ready to accept that my daughter was fine in her world and I am the one who needed to change to make sure I gave her the love and support that she needed to navigate around my world.

One thing though I did not have to worry so much about was: Do I have the correct basals set to deal with the stress and emotional roller coaster that came with our daughter’s diagnosis? This is quite liberating and freeing.

AUTO MODE TO THE RESCUE

Through this time, Auto Mode worked like a champ and I can undoubtedly say it has done a better job of adapting to all the stressful events of 2018 than I would have done if it was left to me in Manual Mode.

I no longer have to worry so much about lows when taking my daughters to two separate schools or doing yard work. (I had been diagnosed with uncontrolled severe hypoglycemia in 2013 when I got my first pump. I am also a late onset Type 1)

Despite Auto Mode’s many shortcomings that could keep you awake all night, I am glad that I never gave up.

WITH AUTO MODE PATIENCE IS KEY

This is my advice: If you are thinking of giving up on Auto Mode because of all those highs that you can’t seem to control, just give it time. For me it has taken close to a year to finally get to where I am comfortable with my numbers.

The Auto Mode algorithm seems to be more adaptive than I even thought. And the more data you feed it, the better it will become.

 

The perfect storm – pizza, sensor change, and a kinked infusion set canula = readings out of this world!

 

The Perfect storm. New infusion set, sensor, and pizza.

Lesson I learned: At the beginning of sensor life, it might not be a good idea to only depend on sensor readings only.  Also, probably not a good idea to change the Guardian sensor, infusion set and eat pizza close together!


Last night, I had what I would call a perfect storm where I replaced my sensor and infusion set and then ate pizza. Unfortunately, my sensor did not catch up with a sharp rise in blood sugar since it had not stabilized. I only caught the high sugar readings when I checked my meter Blood Glucose (BG) reading.

Read more

Shortcomings of the Medtronic MiniMed 670g, Auto Mode and Guardian 3 sensors

From the onset let me say I think the Medtronic MiniMed 670G and the Auto Mode setting are a big leap forward in glucose control for Type 1 diabetes. Closed loop insulin pump technology is the technology of the future. Personally I foresee the insulin pump becoming an install-and-forget type of medical device in the near-future. While in no way perfect, the first iteration of the MiniMed 670G was a great step forward in this direction.

Read more

“Marinating” the Guardian 3 Sensor – Does it Work?

Some people using the Minimed 670G pump and Guardian sensor have recommended inserting a new sensor a couple hours beforehand prior to the expiry of their sensor they are using (a process they call “marinating” the sensor). In this way the sensor stabilizes well before you have to exchange it out with an old sensor.

I have tried this technique but with mixed results. It has worked beautifully lately but initially a couple sensors completely failed prior to the warm up period. As soon as I inserted the sensors into the transmitter, the green transmitter light did not blink as expected. Neither could the pump find the sensor. Maybe a bad batch?

Marinating helps the sensor signal stabilize quicker after the warm up period, although you still have to pay attention to upper thigh sites (they take longer to stabilize and can lead to major lows once the sensor stabilizes).

Double-Check Sensor Blood Glucose Towards End of Life for the Guardian 3 Sensor

Double arrows pointing down on your pump is never a good thing especially if the number is 65. But towards the end of life the guardian CGM sensor, it is especially important to counter-check this reading against a BG meter reading.

It is quite common for the sensor to yo-yo between lows and highs especially on the last days of its life (displaying double arrows due to false positives and negatives in current readings).

In fact, this instability is normally a signal it is time to change your sensor especially if the numbers do not match BG meter readings.

Decided to counter-check sensor BG before treating low .

A Short Article Review – Optimizing Hybrid Closed-Loop Therapy in Adolescents and Emerging Adults Using the MiniMed 670G System

Link to the Article abstract for this article titled Optimizing Hybrid Closed-Loop Therapy in Adolescents and Emerging Adults Using the MiniMed 670G System by Messer Et al. that was published on Diabetes Care in April 2018. Inbox me to see how we can get you a copy of this paper. Disclaimer.

Bottom line: Your Endo might need to really get aggressive in adjusting your carb-ratios for Auto Mode.


This article is probably the most detailed of any publicly available Medtronic sanctioned studies that actually discusses the MiniMed 670G pump and gives guidelines on how to optimize Auto Mode. It delves a little and provides references on how the HCL algorithm used in Auto Mode works and the inputs that can be adjusted when it comes to Auto Mode.

In their trials, the authors worked on optimizing Auto Mode inputs for 31 adolescent and young adult participants (14-26 years old) over a period of 3 months.

The study provides three settings that can be used to tune Auto Mode, namely: carb to insulin ratio, Active Insulin Time (AIT) and Bolus Speed (although this setting is not used or explained for the trial).

The main takeaways from this paper can be summarized as follows:

Read more

Solution for the Medtronic 670G AutoMode BG Loop

UPDATE 09/10/19 – A new enhanced transmitter to resolve the BG loop issue is being issued to Medtronic MiniMed 670G owners. This has worked beautifully for me since receiving it about 3 months ago.

To request for the new enhanced transmitter follow this link.

Or you can contact your Medtronic Diabetes Educator or call Medtronic directly for one.


Couple weeks ago, I could not enter Auto Mode on my 670G for three days due to the dreaded “BG Required Loop.” As a solution, I eventually had to change the sensor to be able to re-enter AutoMode.

God knows I have tried to resolve the issue using every advise given online in forums (including trying to “fake” the system by entering a number just above or below your last entry) but these have only worked only a couple times.

What I think Causes the BG Required Loop

At issue I think is the way that the 670G calibrates the Guardian sensor. It seems to be programmed to validate the BG you’ve entered into the system probably based on the ISIG history and its predictive model of where your BG readings are trending towards.

Sounds complicated?

Read more

Comparison of the Medtronic Contour next Link 2.4 meter and the ONETOUCH UltraMini

I recently set out to compare the two meters since I like to have a back up meter to the Contour Next meter supplied by Medtronic. It is only until recently that AETNA started to approve the Contour Next glucose test strips through my insurance coverage.

So I have been using the ONETOUCH UltraMini for the last 5 years or so since it was the only meter that was fully covered by my insurance without a co-pay on my part.

The difference in readings was all over the place, but the only discernible pattern was that the Contour next Link 2.4 meter read consistently higher than the ONETOUCH UltraMini.

I personally think that the Contour Next is a more accurate meter (closer to the real blood glucose number) but the ONETOUCH UltraMini is more precise (multiple readings from one site are closer).

And this is important since the ONETOUCH UltraMini and ONETOUCH Verio’s superior precision is  key to reducing Auto Mode and sensor errors and especially eliminating the “BG Required Loop” that occurs in Auto Mode.

Read more

Kicked Out of Auto Mode….Again!

Guardian Sensor Stability and Auto Mode

I have been trying to get back to Auto Mode for the better part of the day today.

As you can see my readings in manual mode were not so bad and I would say those were stable sensor readings. I am not sure what reading variance the Auto Mode algorithm considers acceptable to enter Auto Mode.

Variance does not look too shabby but Auto Mode did not like it.

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Review – What I Love (and Hate) about the Minimed 670G Auto Mode Feature

The MiniMed 670G in AutoMode. The blue shield means it is all-systems-go and in AutoMode.

The MiniMed 670G in AutoMode. The blue shield means it is all-systems-go and in AutoMode.

There is a lot to like about the Auto Mode feature for the Medtronic MiniMed 670G. This feature is analogous to self-driving technology where a car employing this technology drives along fine until the camera hits a blind spot. The same happens for Auto Mode, it works fine until an unexpected situation arises and the Auto Mode algorithm cannot handle this sudden change.

The closed-loop hybrid system is ground-breaking technology that as a research scientist I really appreciate. Yes, it is a work in progress. But its current intricacies and potential to give people with Diabetes better control of their glucose numbers and more freedom to pursue other important things in their lives is really laudable.

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Tunable Settings in Auto Mode for the MiniMed 670G

Tuning Auto Mode for the Medtronic MiniMed 670G is just like tuning an engine. Changing one setting throws off the other settings

Getting Auto Mode settings just right seems to be a balancing act – more fine tuning than just dialing settings up or down

UPDATE - I have certainly found out that dialing the Carb Ratio and Active Insulin time up and down do not necessarily mean that you will get better control. That is why it is important to work with your endo or educator to tune these settings.

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When it comes to Auto Mode for the MiniMed 670G, tuning the settings to get as close to your sugar targets feels a little more complicated as compared to the manual mode. This is because the closed loop system has a feedback mechanism which will likely throw-off one setting when you change another.

In the course of your day, the system is performing a balancing act between bolus and basal to keep you as close to Auto Mode’s fixed and preset BG target of 120mg/dL by introducing a third input – the micro bolus.

When it is all said and done, the user has control of two settings only, namely Carb Ratio (CR) and Active Insulin time (AIT).

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Two Must-Have Books for people on Insulin or Pump Therapy

When moving to pump therapy, the idea of basal and bolus and how you use them in tandem does not make a lot of sense at first. There’s little to using long acting insulin such as Lantus than just injecting and letting it do its thing as far as your basal insulin is concerned.

But since your pump uses a short-acting insulin, you have to supply your basal insulin very small doses to mimic a long acting insulin 24 hour dose.

Getting your basal pump settings tuned is the foundation for successful pumping. In most cases you will need more than one basal rate to deal with uneven insulin requirement in the course of the day.”

The following two books have been indispensable books for me as I have tried to set basals, carb ratios, active insulin time etc. When I was first diagnosed, I struggled a lot with severe hypoglycemia.

“Think like a Pancreas” is probably the best book out there for optimizing your pump settings.

But reading Gary Scheiner’s book, “Think like a Pancreas” was just an eye opening experience. (See it on Amazon). This is the first book I would encourage anyone considering pump therapy or having trouble with BG control with their pump to get.

It might be the only book you will need to get up and running. Gary offers a myriad of real life scenarios and chances you’ll find a scenario that fits your case.

But if you want to delve deeper into the intricacies of the Insulin pump therapy, “Pumping Insulin” by John Walsh and Ruth Roberts will do the trick.

Recovering from the “Sensor Updating” Message

Every now and then you will get this dreaded message on your Medtronic MiniMed 670G:

Do not Calibrate. Sensor Updating. Do not Calibrate. Sensor Updating. This could take up to 3 hours

In most cases the sensor updating message comes on because I have entered consecutive meter BG readings that the sensor does not like.

You know that chances this will mean that you have to replace your all-valuable sensor when it is all said and done. I have not had so much luck with the “updating” part. Almost always the story ends with “replace sensor.”

As a matter of fact if I get this error towards the end of life of the sensor, I will just change the sensor than wait for 3 hours.

What i do when i get the “sensor updating” message

To salvage a sensor that is only a couple days old (around 4 days or less), I disconnect and then reconnect the sensor following the procedure below:

  1. Very carefully remove the tape and completely disconnect the transmitter just like you during sensor change-out.
  2. Charge the transmitter once again.
  3. Remove the transmitter from the charger.
  4. Reinsert the sensor and start a new connection and go through warmup under
    Options>Utilities>Sensor Settings>Sensor Connection>Start New Sensor.

Morning Meter Fasting Glucose is much higher than Sensor Glucose

As you can see my morning fasting glucose numbers are running higher than I would like them. I feel well rested in the morning if my numbers are below 120. Above that I wake up feeling tired. I have also noticed that it is in the morning that I get the biggest differences in reading between the Minimed 670G pump Guardian sensor and my BG meter (during other times the readings are within 10 mg/dL of each other but in the morning closer to 20 mg/dL ). Not sure why the sensor consistently under-reports my BG readings, but it is at this time that I would love my sensor to be the most accurate! Most probably it might have to do with the fact that the Auto Mode algorithm is likely most conservative at night.

Upper Thigh Sensor Insertion Sites are More Accurate than Belly Sites

Bottom-line: For accuracy and fewer calibration errors I have found upper thigh sensor insertion sites better than belly sites. These sites take longer to stabilize (about 12-24 hours) but always give me very good accuracy and fewer calibration errors over the life of the sensor. Sensor values seem to match better with meter values for the upper thigh sites over the belly sites.


During my pump training, I was told that Medtronic now officially recognizes the outer side of the upper thigh as an FDA approved insertion site for the Guardian sensor. This was not the case for the Enlite sensor.

To shorten the time it will take the sensor to stabilize and enter Auto Mode, some people suggest inserting a new sensor and leave it in place a couple of hours prior to replacing the current sensor. I have had mixed results with this approach.

Rechargeable Batteries Work with the MiniMed 670G

Sanyo Enloop Rechargeable AA batteries I use with the MiniMed 670G

Sanyo Eneloop Rechargeable AA batteries I use with the MiniMed 670G

I never had luck using AAA rechargeable batteries with the MiniMed 530G. For some reason, the 530G found the batteries not to have enough charge even after I had recharged them completely. Since I started on the MiniMed 670G, I have been using Sanyo Eneloop AA Rechargeable batteries with no issue. The batteries might not last as long as the non-rechargeable ones but they last long enough before they are fully discharged. 

How Do Guardian/Enlite CGM Sensors Work?

Continuous Glucose Monitor

Continuous Glucose Monitoring (CGM) sensors are finicky, expensive and we all know of how much of a process it is for Medtronic to replace faulty sensors. For me, changing Medtronic CGM sensors is a ritual I do not look forward for many reasons. Getting my sensor inserted and working correctly seems to be a hit-or-miss proposition.

But the delicate nature of sensors is due to the fact they are miniature electrodes that are affected by small changes in the environment around them including small movements or presence of interfering chemical substances.

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