[IP] Dexcom CGM - First Week Impressions
Thanks to Tom Beatson and Tom Chafin for responding to the CGM
I was under the mistaken assumption that the 3 CGM manufacturers all
used the ISIG value. Looking through the list archives and the pre-CGM
notes I have been keeping, it appears much of the advice given has
been from an MM CGM perspective. Am I the only Dexcom user on the list?
In the last week or so, I have re-educated myself to a Dexcom
perspective. There are many similarities but in the Dexcom world (and
also Navigator), there is no viewable parameter analogous to ISIG.
Dexcom explains it by saying that with the 3 day FDA approved MM
sensor life, it is more critical to have a secondary measurement of
sensor function, especially when the user extends the sensor life. I
can however appreciate the value of the ISIG measurement, especially
if a person is trying to approach the sensor life records of Nikos
Today makes 1 week using the Dexcom Seven CGM and I would like to
share some impressions.
1. I decided not to wait for the Dexcom training and started using the
CGM before my Dexcom training session. I viewed the excellent
instructional presentations on the Dexcom web site and installed the
sensor without any problems. When I eventually met with the Dexcom
trainer, I was able to use the session to discuss more advanced CGM
topics rather than discuss start-up.
2. I have settled on a 3 time per day calibration schedule (morning,
mid-day and night). The Dexcom requires calibration at least once
every 12 hours or else it will give the calibration needed warning.
The 3 times per day keeps me from ever seeing this screen.
3. The Dexcom seven day sensor has been giving me good readings from
day 1 and it continues to do so on day 7. After the 2 hour
initialization, most of my readings have differed less than 10 points
from the One Touch Mini I use to calibrate. I did have one case where
the meter and Dexcom differed by 32 points, but this was after a 100+
grams of carb meal and my BG was changing fairly rapidly.
4. I have not had problems with sensitivity to the adhesive thus
far. One edge of the sensor patch is starting to peel but was easily
fixed with a little Skin-Tac. Even though I applied Skin-Tac to the
site before applying the sensor and have had no problems, the Dexcom
trainer warned me that they don't recommend putting Skin-Tac/ Mastisol
on the skin since it can coat the sensor. The better method is to
apply the Skin-Tac directly to the patch before installing the sensor.
I will do this next time.
5. I am going to extend the sensor to 10 days since I am still getting
good readings and I do not feel any irritation at the site. I don't
know yet if this is a one time 10 day venture or if I will settle back
to 7 days. Dexcom says that they also have data on 10 day use of the
sensor, but they only sought FDA approval for 7 days. She warned me
that if I extend, not to go much beyond the 10 days since the Dexcom
sensor dies a slow a death with the only symptoms being erratic
readings. This is where ISIG could be of value.
6. My biggest concern is about the accuracy of the numbers I am seeing
on the Dexcom, or any CGM for that matter. I will address that it in a
Dx'd 1967, Pumping since 1/14/2004 w/ Animas IR1000, Animas IR1200,
Animas 2020, Dexcom 2G (1/25/2009)
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