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Re: [IPk] Pump +



Hi Pat,

Close....

These days a distinction is being drawn between 'blood glucose monitoring' 
and 'CGM' because CGM in fact does not measure glucose in blood per se. CGM 
measures glucose in interstitial fluid, the fluid between cells.* For the 
past 20-odd years 'blood glucose monitoring' at home has meant _capillary 
blood_ glucose measurement. The diabetes care community has declared the 
fingers, earlobes, and toes to provide dead-on reliable glucose measurements 
(even though capillary samples do lag several minutes behind arterial blood 
samples, but you can't really expect people to take an arterial measurement 
several times a day at home can you). The word 'near' seems to be dropping 
out of common use ('near continuous glucose monitors' --> 'continuous 
glucose monitors') for some reason (perhaps marketing?).

The lag time between CGM and a fingerstick seems to me to be pretty similar 
to the lag time between an alternate-site test and a fingerstick. For all 
the benefits of alternate-site testing (AST), every meter that has approval 
for AST has a disclaimer in the user manual: if you are testing for 
hypoglycemia or you have hypoglycemic unawareness, test on your finger. It 
is also not advisable at this time to dose insulin based on a result from 
AST if you aim for quite tight control - this is because the glucose level 
that your forearm reflects may tell you what your finger would have said 
about 20 miins ago. If your glucose level is changing quite rapidly, your 
arm may say 7 mmol/L at the same instant that your finger would say 5 
mmol/L. If you dosed your insulin based on the 7 mmol/L number when you were 
really 5 mmol/L, you'd have a hypo.

The two best things that I have seen from non-blinded (real-time results) 
CGM are these: 1) trending data: which direction is my glucose going and how 
fast, which means even if the CGM reads higher than my finger, it can tell 
me that my glucose level is shifting rapidly; and 2) what the heck happens 
overnight. One night I went to bed with a glucose of 5.4 mmol/L and woke up 
with a glucose of 5.5 mmol/L. Hey presto! WRONG. The CGM showed me that I 
had in fact spent most of the night (from 2 hours after sleep) at 10 mmol/L 
and my glucose was just on its way down for a hypo at the time that I woke 
up.

Melissa
Type 1 13 years; MiniMed pumper 7.5 years; Animas pumper 2 years 6 months; 
25 years old today!

*Dorland's definition of interstitial fluid: "the extracellular fluid that 
bathes the cells of most tissues but which is not within the confines of the 
blood or lymph vessels and is not a transcellular fluid; it is formed by 
filtration through the blood capillaries and is drained away as lymph. It is 
the extracellular fluid volume minus the lymph volume, the plasma volume, 
and the transcellular fluid volume."

----Original Message Follows----
From: Pat Reynolds <email @ redacted>

In message <email @ redacted>, Melissa P. Ford
<email @ redacted> writes
 >CGM technology is the generic category of which CGMS is one type of 
product.

Hi Melissa,

Is a (or one) 'GGM technology product' the same thing as 'a near-
continuous (invasive) blood glucose sensor, which can either give real-
time read outs, or be downloaded for later study?
[snip]
Cheers,

Pat
.
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