CGM Sensor Stretchers

[tim2000s]

if you consider "libre" works in past way (past information), it only works 16 hours per day (when you sleep, it doesn´t work...), it lasts 14 days, but I think 90% dexcom users get 2 to 4 weeks (personally I always get 2 weeks, some 3, but I always replace it in 2 weeks)

Again, I think you misunderstand the Libre. The Libre captures data in the same way as a "blind CGM" from Medtronic does. When you sleep, it still captures data and gives you the information about what happens overnight. It doesn't alarm, no, but it does provide you with continuous data.

Based on the conversations I've had with people on Facebook on a group that is all about CGM, Dexcom users typically don't get more than two weeks out of a sensor, and more importantly, the data quality of the sensor after about 14 days is reduced as the Glucose Oxidase enzyme becomes much less effective. If you look at the topic here, you will see the cost of the Dexcom and Libre over two years are roughly comparable only if you get four weeks per sensor. If you get the more average two weeks per sensor, the cost of dexcom is significantly larger (roughly 1.8x the price of the LIbre).

I hope next "libre" will be released with alarms and automated read (it´s very easy... a wireless NFC device programmed to read every minute and transmit to receiver).

As pointed out above, the cost of the two systems is very different. As soon as you introduce a transmitter into the sensor you need far more power - that's a huge benefit of NFC. NFC doesn't have the range for a permanent feed so you would need an alternative.

Alarms are only beneficial if you need them. I don't as I have hypo (<3.9) and hyper (>9.0) sensations that indicate that there is something up. In addition, with the Libre I get 24 hour x 7 day data showing what my blood glucose is doing. This is the most useful data possible as it allows full details of what I am doing to be observed and allows me to gain insights into my diabetes.

Taking the costs into consideration, in the first year of using a Libre it will cost me £1290 for a huge amount of insight into how my diabetes works. If I want the same thing from Dexcom I pay £2825.

However you look at it, if I don't need alarms, then I get the same information from a Libre for less than half of what I'd pay for a Dexcom. That's why doctors (and the public) like it. It changes the cost paradigm for continuous glucose monitoring.

I respect that there may be other reasons for wanting or requiring the Dexcom, but unless you have fully assessed the Libre, I think you haven't understood what it really does.

 

[pablodr]

Hi Tim2000s. To me is a bit difficult explain I would like (my english isn´t very good), I hope you forgive my mistakes.

Really I understand perfectly how libre works (I can´t use, of course because I have "libre" (free) life, not good to me, but I have friends with dexcom that tested it and share to me, and don´t like...). Look... all people with libre likes dexcom... a lot (near all) people with dexcom, don´t like libre (don´t like if they have to use). Then we are talking about one point, only: cost, not performance, no reliability, no quality life, no "free life".

How you say, it captures data ie when you sleep, but that information isn´t usseful, because it´s past information.

With dexcom (or navigator II, but I talk about dexcom because it´s most popular) you have all information too, but difference it´s device interpretes it.

If you are sleeping with libre, you can get hypo or hyper, you don´t know, only next day when you check in morning (if it´s hypo maybe you noticed, but it´s bad)

That information only is usseful to "live" as diabetic, planing next day to avoid it (and it isn´t possible always). With alarms and real time control, you can live near to "non diabetic". You know how are you now, before and you have tendences. All in real time. You can forget your diabetes and only check when your device BEEP, if not BEEP, all ok... and of course, big increase or descent (dangerous) are advertised (alarm), levels (alarm). you are protected. It´s main difference.

In "libre" you must interprete that data... with dexcom, you can too "interprete", or only "use" it.

With strips, too, you must interprete data (I was using 10 strips/day before dexcom). It´s a hard job. With dexcom, you don´t need do it. Follow the device. To me works, but how you say, maybe not ok to all people.


Dexcom sensor life, in my experience and group it´s usually from 2 to 4 weeks, only 2 persons gets under 2 week, most people get 3 weeks (consistent) and some (3 I know) get 4 weeks usually.
I´m talking with good performance. I get 2 weeks, because I discard sensors directly at 2 restart. I can continue using it, but how you say, performance is bad, and if I need real time monitor to live, then, it doesn´t work how I need. Directly discard working ok (of course, performance low a bit, how first day).


I understand maybe not all people need or want "real time" monitor. But problem to me is LIBRE device is bad. Is bad due technology is obsolete and expensive.
From near years ago, dexcom is working with seven plus with a fantastic performance. Over libre (dexcom does all libre... and a lot more... libre does a bit things only)

and now, 2015 appear "libre" how fantastic technology... to me, it´s a fake. where is improvements?

cheap? (without real time control, no automated... no alarms... no "protection"... it´s only replacement, to me, for strips)

In fact, in Spain, doctors talk about this device will be paid to people (how I before dexcom) need 5 strips day or more, only because it´s cheaper.

libre... and "free" (of charge), great¡¡¡ fantastic. I like better strips. Pay (less dexcom of course), no, to me is expensive.

Future isn´t "libre" of course... future is real time control (alarms, arrows... all automated. You can´t work for your device... your device MUST work for you.)

Since I have dexcom, I forgotten my diabetes, no hypos, no diet, no "time hours", free life. Of course I could get a fantastic control with dexcom, my hba is "normal", "standard", "medium", not good... not bad... 7-7.5 hba... but considering I don´t know count hidrates (I forgotten), no hours, absolutely free to eat, to sleep, to... (and no hypos¡¡¡)... I´m happy and I live very good.

with "libre" I can´t live in this way. Not cheap then.


About prices I must say DEXCOM is working always to get more money.
I´m using old SEVEN PLUS (yes, it´s outdated, no spare sensors -I have, expired but they works perfectly, even 4 years expired- but you get same performance G4... not colour screen, not melody sounds... but performance it´s same, they do same. But transmitter in G4 get 6 meteres distance range, but 10 months life... seven plus get 1.5meters and 2.5 to 4 years (I´m using a near 4 years original transmitter now). And of course, you can replace batteries (pay to dexcom it´s a crime, they know... they can offer rechargeable battery but don´t).

I would like dexcom offer a LOW COST AND CHEAP (how "freestyle libre") and it´s very easy: old seven plus with disabled alarms (change a bit from 1 to 0, only) at same price libre... and it would be better.

"libre" to me is a strips replacement, and only a "marketing" product, good because it´s "cheap" (but not as cheap how some think). But end of libre is be FREE, to pay, real MGC it´s correct, even more expensive.

To me, of course, to me.

Regards and sorry for my mistakes¡¡¡¡

 

[Spiker]

Good idea to suggest Dexcom offer the Dexcom 7 at a lower operating price.

I did not see deterioration of accuracy on my G4. In terms of the difference vs finger stick calibration it would stay constant for at least 4 weeks. At some point after that it would suddenly start to diverge from fingerstick tests and then you have to chuck it. But often as not the sensor is gone before you get to that point. Usually it has just fallen off.

 

[Spiker]

Regarding the alarms. I have on a handful of occasions been helped by a hypo alarm and only once or twice was that at night. I tended to sleep through all alarms at night in fact. So the only really useful alarms were the daytime hyper alarms. Those did help get my average blood sugar down, call attention to very spiky foods, etc. But in large part I could get by without the alarms and be quite happy still.

 

[tim2000s]

@pablodr I understand your point, and if you need the alarms because you need to know when going high or low, then great, the Dexcom is for you. It announces to you in real time that your glucose level is hitting a level that you need to do something about. I have other mechanisms that let me know about that.

In the meantime, the Libre offers those of us who weren't able to fund Dexcoms, because they were far too expensive up front, the opportunity to track what our glucose level has done over the period in which we look at the graph. The simple act of scanning the reader over the sensor, or looking at the Dexcom without an alarm going off is no different to finger pricking. And we all still do this. What the Libre gives you is not "just a replacement for finger pricking" but also an ability to properly track what has happened to your levels, which is also available from the Dexcom.

Ultimately I agree that the technology will develop into a closed loop feedback model where input it limited from the user, but for now, the Libre is a very good way to get into CGM in order to understand what really happens to blood glucose levels, which is the reason why the majority of people have bought it.

 

[Diamattic]

I have been using my Dexcom G4 with my Vibe for a while now, and have managed to get 21 days out of all three of my dexcom sensors.

Each one could have been worn longer - obv an unknown amount - but at 21 days i decided to remove each one because at around day 15ish they start giving me the '???' occasionally, and i find they react much slower to BS changes as time moves on, to the point where they don't quit catch everything.

So far so good! I am happy to say that i have been getting consistently 3x the wear life Dexcom promised without issue!

 

[Pete R]

Hi,
I'm new to the forum and have had a Dexcom G4 platinum for about four months now. I'm astonished by the longevity of the sensors reported here. I'm getting reliable results for the first 7 day sensor life then intermittent ??? for the second 7 days usually with deterioration to a non-useful extend towards the end of that time which is really frustrating.
Is there something I'm doing or not doing? I'm pretty lean and cycle competitively so I'm wondering if the location of the sensor or the body composition (pretty lean) has any influence. I've followed this tread and can't see anything obvious.
all the best, Peter

I'm 47, have had Type I for 37 years and use a medtronic pump.

 

[Spiker]

Hi Pete and welcome.

If you are lean (and very active) it may be you are getting movement of the sensor canula inside the opening into your body. Try to place it somewhere where movement and vibration are minimal. And strap it down well with tape etc.

 

[Diamattic]

Hey Pete,

I have no issues with cycling in my sensors.

Are you just inserting the sensors and leaving them? In order to get extra life i have to apply another layer of protection over the stock adhesive pad to shield the stock pad from water, and deterioration. I have to carefully replace my extra layer every 4-6 days otherwise it looks pretty gross and risks peeling off and taking the dex pad with it.

Without an extra barrier after about 7 days the stock sensor pad stretches and no longer makes a tight fit on the skin which will cause the '???' you reported.

Its all about shielding the stock adhesive as long as possible i find.

 

[Pete R]

Hi Spiker and Diamattic,
this is great advice for me thank you both. I'll try the recommendations and see how things go. I've ordered some of the Opsite flexifix I saw recommended to help secure the sensor.
Diamattic, I find that the interstitial fluid measurements of the cgm systems always lag behind blood test when riding. I think unless blood glucose goes above optimal it goes straight from the stomach into the bloodstream and prioritised to the working muscles to an extent. For example, I was training 5 hours at a fair pace on Saturday and the cgm was alarming for the first 2 hours despite having optimal blood glucose levels. The team-mates I was with thought I had a reversing alarm on the bike when the dexcom was bleeping away! I don't know if this happens with other sports or what your experiences are.

thanks again,
Pete

 

[Spiker]

That is really interesting Pete R. I have a pet theory that glucose rich blood is preserved where it is needed and not in the peripheral tissue where we read BG from. No evidence other than anecdotal - eg a few days ago I read 1.8 mmol/L but I certainly was not in a coma or even feeling particularly bad, just a mild hypo sensation. Happens a lot that I get "impossible" fingerstick BG even when I am not low carbing.

 

[tim2000s]

That is really interesting Pete R. I have a pet theory that glucose rich blood is preserved where it is needed and not in the peripheral tissue where we read BG from. No evidence other than anecdotal - eg a few days ago I read 1.8 mmol/L but I certainly was not in a coma or even feeling particularly bad, just a mild hypo sensation. Happens a lot that I get "impossible" fingerstick BG even when I am not low carbing.

I'm not sure that blood is preserved, as that would require some form of pooling mechanism. I think what is more likely is that glucose is removed from the blood by the muscles/organs that need it such that when it reaches the peripheries, it is at a lower level.

 

[Spiker]

I'm not sure that blood is preserved, as that would require some form of pooling mechanism. I think what is more likely is that glucose is removed from the blood by the muscles/organs that need it such that when it reaches the peripheries, it is at a lower level.

Good theory - so the brain, organs and muscles are just "first in the queue" ahead of the peripheral tissue.

 

[tim2000s]

Good theory - so the brain, organs and muscles are just "first in the queue" ahead of the peripheral tissue.

It's kind of in line with the difference between exogenous and native insulin - exogenous insulin acts initially on muscle tissue, which becomes the primary filter of Glucose from the blood, unlike a healthy individual for whom the liver undertakes 70% of this job following release of insulin into the hepatic portal vein.

 

[Diamattic]

That is really interesting Pete R. I have a pet theory that glucose rich blood is preserved where it is needed and not in the peripheral tissue where we read BG from. No evidence other than anecdotal - eg a few days ago I read 1.8 mmol/L but I certainly was not in a coma or even feeling particularly bad, just a mild hypo sensation. Happens a lot that I get "impossible" fingerstick BG even when I am not low carbing.

I am not sure if i can agree with this or not. But i have had alarms telling me my BS are in the 1's and low 2's so i would rush to check my finger and find they are actually in the 5s and 6s.. I think the Dexcom is just plain wrong sometimes.

Hi Spiker and Diamattic,
this is great advice for me thank you both. I'll try the recommendations and see how things go. I've ordered some of the Opsite flexifix I saw recommended to help secure the sensor.
Diamattic, I find that the interstitial fluid measurements of the cgm systems always lag behind blood test when riding. I think unless blood glucose goes above optimal it goes straight from the stomach into the bloodstream and prioritised to the working muscles to an extent. For example, I was training 5 hours at a fair pace on Saturday and the cgm was alarming for the first 2 hours despite having optimal blood glucose levels. The team-mates I was with thought I had a reversing alarm on the bike when the dexcom was bleeping away! I don't know if this happens with other sports or what your experiences are.

thanks again,
Pete

@Pete R - I went to my local drug store and purchased the BSN clear medical bandage roll for around 8$. I cut my own rectangles (with rounded corners) and then cut a rectangle out of the center so that the sensor will slip through and still be snug. The reason its snug is the stock pad does get wet, or loose around the base of the sensor and shorten its life.

As i said i replace this patch about every 4-6 days depending on how much wear it gets from working out, showering, scratching, etc.

And yes. Dexcom has published saying the sensors lag 5-15 minutes behind finger sticks, depending on the rate your BS is changing. They also have an 14% error margin. So a real reading of 5.0 has equal chance of displaying as 4.3 or 5.7. This means if your BS is hoovering around 4.5 you MAY get plenty of low alarms since its detecting you below 3.9 when in reality its not that low.

I have read some papers that moderate excercise will lower BS's where any training that pushes your VO2 Max above 80% would increase your BS as your liver is triggered to pump out glucose. I have posted that journal paper on this site somewhere in the past, your would enjoy it. It was written by a Canadian professor at York University in Toronto who is also a Type 1 Diabetic and cyclist - Most of his research is how diabetes and exercise interact. His name is Dr. Riddell - http://www.yorku.ca/mriddell/index.html

 

[Spiker]

I am not sure if i can agree with this or not. But i have had alarms telling me my BS are in the 1's and low 2's so i would rush to check my finger and find they are actually in the 5s and 6s.. I think the Dexcom is just plain wrong sometimes.

Maybe, but that's a separate issue. I am talking about fingerstick tests below 2.0.

 

[zjed]

How do you tell when your sensor has had it?
I'm still on my 1st sensor (12 days), I'm seeing a few 'scattergun' areas when readings are moving up/down by 1-1.5 mmol for 1/2 an hour or so before flattening out again.
I also get the odd single reading @ around 2 mmol then goes back to where it was on the next reading, all the alarms go off, usually happens in the middle of the night.
I was banking on 2 sensors a month, not sure if I'll get there.

I'm also running a little experiment on the dex receiver, I haven't calibrated it for over 3 days now. Trend lines are in sync with xDrip and is currently only 0.2 mmol different, I can't pick any difference from when it was calibrated.

 

[Spiker]

I'm also running a little experiment on the dex receiver, I haven't calibrated it for over 3 days now. Trend lines are in sync with xDrip and is currently only 0.2 mmol different, I can't pick any difference from when it was calibrated.

Forgive me as I don't know xDrip but I believe it's reading the same signal from the same sensor? So isn't this just a case of the Dexcom receiver and the xDrip receiver both being as wrong as each other? Or am I missing something.

 

[zjed]

Forgive me as I don't know xDrip but I believe it's reading the same signal from the same sensor? So isn't this just a case of the Dexcom receiver and the xDrip receiver both being as wrong as each other? Or am I missing something.

My understanding is that the transmitter sends raw data from the chemical reaction in the sensor (which I thought would vary as the sensor gets older).
The receiver interprets the raw data into a BGL with the help of its calibration readings.
So yes, the xDrip and Dex get the same signal from the transmitter but they use their own formulas and calibration data to give you a BGL.

 

[DunePlodder]

My understanding is that the transmitter sends raw data from the chemical reaction in the sensor (which I thought would vary as the sensor gets older).
The receiver interprets the raw data into a BGL with the help of its calibration readings.
So yes, the xDrip and Dex get the same signal from the transmitter but they use their own formulas and calibration data to give you a BGL.

Yes that is correct. Both read the "raw" data but the Dexcom does more of an analysis checking & interpreting the last 2 or 3 readings giving a smoother graph. However if it can't make sense of the readings it shows "???" until it can or gives up. xDrip will show the readings even though they are erratic. Even with poor readings it's often possible to mentally draw a line by eye & get an idea of whether they are dropping, low or whatever. Also the xDrip graph will often return to a good line ages before the Dexcom restarts.

It sounds as though your sensor may be on the way out but it could be that you are dehydrated which affects it. Also paracetamol messes up the readings so best to avoid it. It may come back & give you several more days. Fingers crossed!