The Libre, am I missing the point?

[Scott-C]

Very interesting bit of info Scott. Having used 5 dexcom sensors so far my average life with 4 have been 22 days. Only one sensor hasn't made it this far, 9 days and it failed completely. This just happened to be the week I was struck down with the "Aussie flu ".
Biofouling???? Maybe or maybe not, but would be interesting if it was to happen again.

I've lost track of the link for it, but I read a paper a while back setting out a list of things which conspire against accurate readings. Lots of them, biochemical, bioelectrical, biomechanical. It's extraordinary these things work at all and understandable when they don't

I suppose the trick for those of us lucky enough to be using them is to figure out how to be savvy enough to know when a reading is "right" and when it might be "wrong". Gets easier to do that the more they're used.

There's a pay access paper so haven't read it but the abstract says it looks at sensor development ideas for reducing biofouling. Copied below, it's obvious they don't just buy the bits from Maplins, there's some serious engineering going on here at a microscopic level!

Nine sensor modifications are discussed herein: hydrogels, phospholipid-based biomimicry, flow-based systems, Nafion, surfactants, naturally derived materials, covalent attachments, diamond-like carbons, and topology.​

PS: there's been a libre sensor availability blight recently, so I hedged my bets and bought a dexcom G5 sensor and transmitter just in case I ran short of libre. It's sitting on the sideboard just now, but I'll probably join you dexcommers at some point to give it a trial run (although from some youtube videos, looks like I'll have to learn some yoga and gymnastics to attach it to the back of my arm singlehandedly!).

 

[Scott-C]

My last one definitely had some form of biofoulimg in its last eight hours. Readings crashed from high 7s to Lo in the space of an hour, even though my blood was reading 7s. When I removed it, the end of the filament had some gunk on that I had a real job to pick off. First time I’ve seen that.

There's a paper at the link below discussing how small bleeds near the sensor can cause rapid loss of readings, as opposed to other factors causing a gradual decline. Maybe that's what happened with yours.

http://europepmc.org/articles/pmc3192625

 

[Celsus]

For all those people who think the libre is widely unreliable because it doesn't match up with their blood meter I wonder how many have tested a drop of blood then squeezed out another drop and taken another reading or used a different meter and different test strip?

If you do you might decide your blood meters are pretty unreliable as well and then that becomes scary as you no longer know what to trust. If you use the libre you have to have a reasonable amount of faith in it. There will be times though when a libre sensor may not perform as it it is wise to test bloods from time to time if in doubt and in the first few days.

The longer you can leave the libre in before activitating it the better in my experience. Having waited 4 weeks for our last libre delivery and with my son having run out several days previous the libre was inserted and started up immediately. For a good 6 hours afterwards it was reading 2 - 3 below our blood testing and spent the majority of the time saying low whereas blood were generally between 4.5-6. By morning it was reading a figure and much more in line with blood readings.

100% agreed - its fun to read how others think the fingertip bg test is accurate. (And implicit therefore the Libre should show the same for that also to be considered accurate).

As you say, even when using the same meter for fingertip tests, your result will/can vary wildly when taking from left hand versus right hand, even between fingertips on the same hand! And then more so if you try and take a zap of blood from a main artery versus from one of your extremities.

I am happy that I do not live in the UK, as only using Libre now for all my checks. The old meter was thrown out after just 3 weeks or so when starting with the Libre. Never had an issue with 'wrong readings'. So maybe I am just one of the few lucky ones, but it definitely works perfectly for me! Yes, when plugging in a new sensor every two weeks, they tend to need a little 'warming up'. But as with everything-diabetes, with a little proper planning in advance, everything is possible!
(I always switch on Saturday mornings just after having had breakfast, so cool to go for 2-3 hours before needing a super accurate reading)

Btw, another subject where I could start to challenge some of the 'healthcare professionals' regarding Libre is that I do certainly hope that they are not fiddling around with the many intriguing parameters available to the medical staff that you have on it? As that WILL screw up its accuracy if not knowing very well what you do! You find them on the meter within the 'Professional Options' area in the reader settings. And normally patients should not have access to this. Using the device straight out of the box using the factory set parameters should be the default way of using it. But it could be interesting to check if that is the case for those patients that have experienced a high degree of inaccurate readings using the Libre.
Its just a piece of electronic and these do at times get out of whack. E.g. like when you have to make a cold master reset of your iPhone to get it back to be able to make phone calls.

 

[EllieM]

There's a well known aspect of cgm called "biofouling", where foreign body defence mechanisms, biological detritus can clag up the sensor filament meaning that glucose around it just can't get to the sensor to be measured.

Well, my libre gave me excellent results for 8 months and only became problematic when I developed an allergy to the sensor..
I guess the skin irritation on the surface was probably accompanied by irritation round the sensor?

 

[Scott-C]

Well, my libre gave me excellent results for 8 months and only became problematic when I developed an allergy to the sensor..
I guess the skin irritation on the surface was probably accompanied by irritation round the sensor?

What might be going on is that if there's inflammation through an allergic reaction, repair cells are sent out to repair it, they don't march on an empty stomach, they use glucose as energy to do their job, like pretty much every other cell in the body, so they've eaten it before it can get measured, so it appears as lo locally to the sensor.

I haven't done any science since secondary school maaany years ago, but got curious about the science behind it after using libre, so read up a bit about it - could be totally wrong on what I've just said, but it's a possible candidate.

Shame about the allergy, Ellie. I picked up a second hand copy of "Wiley - in vivo glucose sensing" for 20 quid off ebay, it seems to be the go to reference book for cgm developers. There's a bit discussing the adhesive issue. It called it, "non-trivial". A polite way of saying, "really f*cking difficult". You'd think it'd be easy just to get a glue to stick something on for a while, but there seems to be a fine balance to getting it right: too weak, it falls off, too strong, people will be allergic to it. There's been stories of both happening episodically throughout this here forum, so I reckon that Abbot have been changing the glue, but it seems that they're never going to find one which suits everyone.

Fingers crossed, touch wood, I've been ok with the current formulation, but I realised pretty quickly after getting the blucon without thinking about how to attach the **** thing that I'm definitely allergic to (a) DIY masking tape, (b) electrical insulating tape, and, surprisingly, (c) medical tape. Ok with me molnlycke mepore plasters though, whew!

 

[LooperCat]

@Scott-C have you tried gaffer tape?

 

[Scott-C]

@Scott-C have you tried gaffer tape?

I tell ya, Mel, when I picked the blucon up from the post office, I was so keen to see pretty little numbers on my phone, instead of that so passe scanning stuff, if there had been some gaffa tape in the house, I would have used it!

I've not been allergic to anything since my aunt's cat at the age of 5, so I was really surprised by how badly the various tapes worked out: healed up ok, but there was aa blood clot on top of it, like an actual wound.

Gaffa tape and clingfilm were briefly discussed in @maglil55 ,s magnificent Life with Libre thread when she was looking for a way of waterproofing libre for long swim sessions.

She came up with a possible solution (hope you don't mind me nicking the pic from your thread, mag, it deserves to be shown again cos funny!).

https://www.diabetes.co.uk/forum/threads/life-with-libre.118450/

 

[maglil55]

I tell ya, Mel, when I picked the blucon up from the post office, I was so keen to see pretty little numbers on my phone, instead of that so passe scanning stuff, if there had been some gaffa tape in the house, I would have used it!

I've not been allergic to anything since my aunt's cat at the age of 5, so I was really surprised by how badly the various tapes worked out: healed up ok, but there was aa blood clot on top of it, like an actual wound.

Gaffa tape and clingfilm were briefly discussed in @maglil55 ,s magnificent Life with Libre thread when she was looking for a way of waterproofing libre for long swim sessions.

She came up with a possible solution (hope you don't mind me nicking the pic from your thread, mag, it deserves to be shown again cos funny!).

https://www.diabetes.co.uk/forum/threads/life-with-libre.118450/

View attachment 25835

Not at all. Took a while to find that one
I still use Tegaderm and have had no issues with it.

 

[kev-w]

Gaffa tape and clingfilm were briefly discussed

A thumbs down for the cling film here , I 'sawed' a roll up so I could have a piece the size I wanted, wrapped my arm heavily in it over the Libre and the second length I swam it was trailing by my feet, I'm looking out for some shrink wrap next although Tegaderm seems ok.