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    « Is the Grass Not So Green? | Main | Guardian RT vs Paradigm REAL-Time System »

    Continuous Monitoring: In a Sentence

    This post comes from the category of "posts that never quite made it..." since the information in it and the intention to knock it into shape, has been hanging around for quite a while, but somehow it never quite happened. The original title would have been "Guardian RT: In a Single Sentence".

    I guess, it has never been my intention to discuss the Guardian RT or continuous monitoring in great depth since so many others have already made an admirable job of this task: Life After Dx (of course!) discusses use of the RT, Tiffany over at Candid Diabetes has done a fantastic job of describing her experiences with the Medtronic 522 integrated pump and sensor, and Amy at Diabetes Mine  is recounting her experiences with DexCom, following in the footsteps of the Insulin Factor's Matt Vogel. In short, there are plenty of capable voices out there.

    I still wanted to take the opportunity though to try and sum up my perspective on the Guardian RT, which I used for just short of two months before my switch on Monday to the 722. This really is my perspective and my opinions and experiences. Continuous monitoring is definitely an area in which your mileage may vary. But, if I had to use just one sentence to describe this thing it would be:

    The Guardian RT is a device that gives you prompts to test your blood sugar.

    There is obviously more to it, but ultimately that, for me, is what it all boils down to. The Guardian RT has been able to replace some of the prompts that my body has no longer been giving me since my experiences with severe recurrent hypoglycaemia.

    Low and High Alarms, or a series of readings that indicate I am trending sharply up or down are things that prompt me to do a traditional finger stick and treat as appropriate. The Guardian RT doesn't have the on screen grpahs and trend arrowns that both the 522/722 and Dexcom have, but scrolling back through the numbers and drawing a mental picture of where my blood sugar was heading was a frequent prompt to act. I couldn't tell you how many times in the last two months I've tested at times I would otherwise not have, particularly in the absence of prompts from my own body in the form of hypo symptoms, and I have found lows needing treatment and highs worthy of correction.

    I've tended to find that the Guardian RT is spot on with my finger stick readings more than 90% of the time when the reading on the Guardian lies between 5 and 8 (90 - 145). Even at lower levels the correlation is great, provided that the lower levels have crept on slowly. Otherwise there will tend to be a lag of around 10-15 minutes.  When my blood sugar is above 9 (160), the Guardian RT tends to be almost permanently off the number. These things reinforce that fact that the Guardian is best as an indicator of when to perform a traditional test. A conservative low threshold - around 5 (90) - leads to a test before the Guardian can get too far behind, and hopefully before blood glucose can get too low. Even if the Guardian and a fingerstick are spot on at that time, looking back over the trend on the Guardian and checking the next couple of readings, along with knowledge about active insulin on board and recent food and activity can help decide how to proceed. And knowing that a number of 9 or more is unlikely to be spot on is a definite prompt to test.

    But, for anyone who finds that somewhat disheartening, there is more to it: The discrepancy with high numbers appears to be consistent. That is, the discrepancy is almost always the same. Between 9.5 and 11 (170 - 200), it is around 2mmol (36mg/dL) too low, above 11 (200) around 3-4 mmol (55 - 72mg/dL) too low [Bear in mind I haven't has that many readings in this range] This is really significant, because it means I can predict what my finger stick reading is likely to be based on the Guardian reading. The finger stick is needed to check, but the numbers aren't quite as useless as they may appear.

    In fact, a good way to view the RT, or any interstital fluid continuous data, is removed from the numbers entiriely. The scale it gives out could be in pink elephants for all it matters, as long as you know what the numbers mean for you, and you know how you need to act and when you need to test based on them. Also, in my experience, even if the numbers are a little out of whack, the trend is almost always absolutely spot on.

    I'm happy with that approach right now.

    I totally agree with many of the statements out there - that continuous monitoring is not a magic wand to transform control. It is simply another tool, another layer of information that we can use in our quest to stay healthy.

    To me, it certainly gives peace of mind. It is another pair of eyes to watch over me... prompt me to act. And it clearly shows patterns in a way the snapshot finger sticks can never do.

    And the drawbacks...

    Of course there are plenty.

    In the case of the Guardian RT and the DexCom there is the inconvenience of carrying the bulky monitor around, and the risk of losing that monitor if you set it down somewhere away from home.

    Continuous monitoring gives an awful lot of data and as Allison  has pointed out, there is a tendency to get information overload. Some of the data may even be very surprising. I was totally floored by how little my blood glucsoe spikes after certain foods, having always assumed a spike was there. It takes time to shift the ingrained mindset for dealing with data from finger sticks, even the large number of fingersticks that many people seeking good control perform. There is a very real risk of becoming somewhat obsessional about the numbers and continually checking them out and following them. This in turn can easily lead to frustration when the flat line you aspire to in your mind's eye fails to become a reality. (Get real here: even people without diabetes don't get completely flat lines!) Not all the actions made based on continuous data will turn out to be the right ones and sometimes it is easy to regret intervening in a downward trend when it subsequently spikes up, or vice versa. But then, not every decision made based on any data will be correct.

    On the other hand, there is a risk of becoming over dependent simply on the alarms, instead of listening to your body and remembering to use common sense and judgement. Oh, and checking out those trends!

    Plus... the biggie... despite my discussion of accuracy issues above, things can go awry from time to time and the readings will go out of whack. This may be temporary - related to rapid changes in blood glucose levels not matched by changes in the interstitial fluid, or related to performing calibrations at a time when things are not stable. (I had a tendency in the beginning to want to tell the Guardian that it had got things wrong. "Damn you, stupid monitor. Look, my blood sugar is actually thiiiiis high." This is a mistake. It only confuses the unit more and sends things further out of whack.) Sometimes the sensor in use just seems to be a bit screwy. Either way, you know the solution: test,test, test.

    There is no hiding from it.

    Continuous monitoring won't reduce the number of finger sticks needed.

    Hell, it may even increase the number performed!

    (Coming up: Watch out for my High School Science essay standard 'Compare/Contrast'  on my experience of switching from the Guardian RT to the 722)

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    Thanks for this very informative post about the Guardian. I'll be watching eagerly for the compare and contrast on the Minimed pump.

    Did you notice any differences based on things like the amount of fluids you'd had beforehand, or exercise where your fluids may be down slightly and so the interstitial fluids may be out of whack?

    Hi Caro,

    Very interesting post - I found it very useful.

    It is really nice to be able to read about people experiences, and their thoughts on this new technology.

    Caro, I'm so happy that the Guardian is giving you the information you need to succesfully live your life.

    I am VERY curious to try it. Your comment about "pink elephants" I can understand. Sometimes we get caught up in the actual value when what we really need to pay attention to is the trend.

    I would LOVE all those data points, personally. :)

    Nice post; many similarities between your experiences and mine also, I'm on the DexCom STS CGMS.

    Mistakes I've made:

    -calibrating when not stable
    -failing to take a confirmation fingerstick test

    I've also noted that the number of fingersticks I'm doing is going UP. I'm hoping to reduce the fingersticks as I get more comfortable with the CGMS.

    Best of luck to you!


    How did you manage to get a CGMS in england? I live in england too, not allowed one! did you buy it yourself?

    I'm curious to know what you mean by "not allowed". Who exactly has refused you, and was it the device they refused, or funding for it?

    The technology - at least the Guardian RT - is available in the UK, and has been since December of last year. The 522/722 is having a slow roll out, linked to particular hospitals at the current time, as I understand it. If you want a Guardian RT and can afford the price tag, give Medtronic UK a call and order one. They'll probably want to check with your diabetes team, but if you are paying, your team are pretty unlikely to object.

    And that is just it, you almost certainly would be paying because funding is the current problem. I've been lucky in that I was able to borrow the Guardian RT from a friend, and the 722 has been arranged by my hospital. This is purely because I have had a specific reason for using it following my diagnosis of Addison's disease and severe problems with hypoglycaemia. My consultant has seen the difference it has made to me and is supporting me in its use. I'm paying out of pocket for the sensors though.

    We are in a situation much like the one that existed with pumps until the NICE Guidance was published. I got my first pump prior to that guidance and had to deal directly with the PCT and plead for funding. Without guidance in place it was up to my diabetes team and I to try to make a case the PCT couldn't refuse. The same will now be true for continuous monitoring supplies. There is nothing to stop anyone from applying for funding, but at least until there is a NICE appraisal, the results will be hit and miss at best. And then we have no idea what NICE will say...

    There is one person in the UK who has secured funding for sensors for 12 months.

    This isn't really all that different to the situation in the US. In general there is no insurance coverage for CGM supplies, however there are reports of a few individuals who have made a case and secured insurance coverage.

    It looks likely that the 522/722 will also be sold here as they are in the US and Canada - in two parts. The pump part and the transmitter part. This was done in the US in part because the FDA have only officially approved the CGM part for adults 18 and over, but also because insurance companies would then continue to cover the pump part as it is just an ordinary pump, leaving users with just the transmitter to pay for out of pocket. This keeps costs to the user down from the cost of an entire pump, and so increases sales. In the UK a similar approach means that PCTs will be unable to refuse to pay for a 522/722 pump, if that is what is requested by the consultant. If funding can't be secured for the transmitter, the user will again have to pay out of pocket but only for the transmitter part.

    If Medtronic withdraw the 512/712 from the UK, then convincing consultants to recommend the 522/722 shouldn't be difficult as it will be the only Medtronic pump available. Otherwise the real battle people will face will be with their consultants.

    But then... that is insulin pump therapy all over, now that funding is required by law when requested by a consultant. Forget convincing the PCT, it's all about the docotor in charge of your care!

    Everyone else - Thanks for you comments and compliments on the post.

    I'm loving mine:

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