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RE: [IPk] Medtronic Guardian RT CBGMS

Hi Jane

Today I switched off the alerts, as what I really want is a graph of my 24
hour results, so I can see where I am, or at least where I have been - the
high and low alerts were a bonus to me. I found last night that the sensor
was warning me of a low BG at 4, but a fingerstick test showed 8 or 9. This
afternoon at work, the sensor read 3.3, but finger test said 5.3, which I
was happy with. (I would have eaten at 3.3)

I would be glad to hear how you get on next week with your sensor.
-----Original Message-----
From: email @ redacted [mailto:email @ redacted] On Behalf
Of Jane Halls
Sent: 31 August 2006 12:29
To: email @ redacted
Subject: RE: [IPk] Medtronic Guardian RT CBGMS

Hi Carol,

I had a trial with the Guardian RT a while back. I think it was February 
this year. The first trial ended after about 6 hours because the sensor was 
no longer working. I had to contact the out-of-hours number for Medtronic as

my BG results were way off the RT results and whilst I was on the 'phone the

alert I got said the sensor should be replaced. I had no replacement sensor 
so I had to give up on it. I did get another trial, the following month and,

like you, I had very little sleep the first night! Neither did my husband, 
he wasn't impressed!
I came away thinking that perhaps it wasn't for me. But, as Caroline says, 
perhaps a longer trial may give a better result all round.
Anyway, make the most of it. Good luck.

I have an appointment at Bournemouth Hospital on Monday to have a CGMS 
fitted for a few days to have a continuous reading, without the alerts ( or 
the constant BG results the RT gives). I am looking forward to seeing what 
is going on.

>Hi Caroline - thanks a lot for that. I have really pushed hard to get the 3
>day trial! Did you have to fund your sensor yourself? At the moment I feel
>that my fingerstick tests are telling the sensor what it should be reading.
>The alarms are going off all the time, and I hardly slept last night. I am
>going to try to switch the alerts off, and just let it track my results as
>best it can.
>-----Original Message-----
>From: email @ redacted [mailto:email @ redacted] On 
>Of Caroline Batistoni
>Sent: 31 August 2006 10:56
>To: email @ redacted
>Subject: RE: [IPk] Medtronic Guardian RT CBGMS
>Hi Carol,
>I've been using the Guardian RT for a couple of months. In a way, I think 
>is a shame that you only have the loan for three days, as that isn't really
>long enough to learn how the unit works for you and to get to grips with 
>information the system gives you and how to interpret it.
>It is important to remember that the Guardian RT is *not* a Continuous 
>Glucose Monitor. Rather, it measures the glucose in the interstitial fluid 
>the fluid between your cells. There is a relationship between interstitial
>fluid glucose and blood glucose, which is why the system works at all, but
>the numbers won't always be exactly the same. I think a good principle to
>remember when using a continuous monitor is not to take the numbers at face
>value. The information on the display could be given to you in any number,
>you have to learn what the number is telling you.
>It is also very important not to look at a single number and respond to
>that. The Guardian RT, unlike the sensor augmented pump (522/722) and the
>next generation of the RT itself, has no trend information in the form of
>arrows or an on-screen graph, so you have to manually scroll back yourself
>through the recent numbers and try to draw a mental graph of which 
>you are moving in and how quickly. This information  then needs to be
>integrated with factors such as how recently you ate and how much insulin 
>still active in your system e.g. a sharp rise within an hour of eating may
>well need no action, since it is explained by your meal, and you should,
>provided you have bolused, have the insulin on board to deal with it.
>A couple of other important points: the Guardian will often lag behind your
>fingerstick results due to the lag in the change of glucose concentration 
>interstitial fluid, compared to blood glucose. The faster your blood 
>is moving, the greater the lag will be, particularly with low numbers. For
>this reason the low alert needs to be set very conservatively if you want 
>catch all lows before they happen. This is especially true if you have any
>degree of impaired hypo awareness. The lag with high numbers doesn't depend
>so much on how rapidly your bg is changing, but tends to be more
>predictable. For example, if my blood glucose is over 11, the Guardian will
>usually be around 2mmol behind. If I creep up to around 14, that rises to
>3mmol. This is where 'knowing what the numbers mean' that I referred to
>earlier comes in. I can translate 9's on the Guardian to 11's and so on.
>Again, I set the alert quite conservatively.
>Most importantly of all though: the Guardian does get it wrong. I'm sure
>you've been told to always check with a fingerstick before taking action! 
>my experience, the trend is almost always right, but the numbers won't
>always be.
>Calibration obviously has an impact on accuracy. I, and others, have found
>that calibrating only when your bg is fairly stable (i.e. not after a meal
>or exercise when it may change rapidly) is important. I also try to
>calibrate only at times where the fingerstick and Guardian are in fairly
>close agreement. This may seem daft, but it works. I often have a slight
>"damn you Guardian... you're wrong" feeling and want to feed in the real
>number, but in practice this tends to lead to CAL errors which in turn can
>lead you to having to re-initialise the sensor, which takes two hours!
>I don't know if you have access to the software, but this is one of the 
>useful aspects to me as it allows you to see day to day patterns in the 
>and fall very easily, which along with fingerstick data is great for
>adjusting basal rates or visually seeing the impact of food and exercise.
>Unfortunately three days is not really long enough to experience a wide
>range of experiences to get data on.
>I hope you get some useful information out of your time with the Guardian
>though. It is definitely a great tool and I really think continuous
>monitoring is the future. As newer generation products come out, the
>technology can only improve. We just need to remember to shift our
>perceptions of data from what we have with the 'snapshots' of fingerstick
>If you have any other questions, ask away!
>Type 1 23+ Pumper 4+
> >
> >Is anyone out there currently using one of these monitors? I would be 
> >to "talk" to someone who is - I currently have one on a 3-day loan from 
> >Medtronic rep.
> >
> >
> >
> >Carol.
> >
> >Type 1 nearly 30 years, pumping 1 year.
> >.
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