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[IP] Dexcom CGM - First Week Impressions

Thanks to Tom Beatson and Tom Chafin for responding to the CGM  
calibration question.

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  
separate thread.

Dx'd 1967, Pumping since 1/14/2004 w/ Animas IR1000,  Animas IR1200,  
Animas 2020, Dexcom 2G (1/25/2009)
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