Out of town for the weekend

I hoped to write another post today, but time is running out before I fly to Salt Lake City for the obligatory Labor Day weekend wedding. Here are some topics I'm planning:

* Exercise
* Accuracy - pictures of good accuracy, bad accuracy, and what it looks like after a corrective calibration
* Wearing the receiver, wearing tighter clothes over the transmitter
* Learning curve - little things new users have to figure out for themselves
* More wish-list items
* How to know when the sensor has failed

Any requests?

Wish list: Shorter calibration cable, or none at all

The Dexcom system forces you to use the One Touch Ultra meter for calibration, and a fairly new One Touch Ultra meter at that. Meters manufactured before One Touch paired with Dexcom won't have the calibration ability. My Dexcom trainer sent me a free One Touch Ultra meter when I discovered that the one I already had was too old.

The exclusive calibration arrangement doesn't bother me much, because I like the One Touch Ultra just fine, and even if you don't, the whole point of a CGMS is that you don't have to rely so much on finger stick testing.

Then they make you calibrate with a cable. OK, that feels a little clunky to begin with, but I have been told they will put wireless transmission in future models. The thing that gets my goat is that the cable they make you use is like three feet long! (When I get the chance I will measure the cable and report its actual length.*) Of course anyone using this system will coil the cable and keep it in the case that comes with the One Touch Ultra so it doesn't get lost, but this is a big pain in the neck because that much coiled cable is very bulky and the case is the same little case they included with the meter before the cable was added to it.

What makes it really crazy is WHY on EARTH do they think we need such a long cable? When you calibrate your meter, you are sitting right there, you do the finger stick, you plug the meter into the receiver, wait a minute, and unplug. This could easily be accomplished with a 6-inch, or even a 3-inch, length of cable. The only reason I can think of for such a long cable is to swing it over my head like a helicopter when I get mad about a large discrepancy between the meter and the Dexcom receiver. This is one of those features where you wonder whether they REALLY tested this system on people who have to live with it? I mean I know they did, but still, it's one of those thorns in your side that seems insignificant but makes a difference in daily life.

Wish list item #2: Shorter calibration cable while we wait for wireless transmission.

* Update: Read the first comment on this post. Bernard reports that the cable is 6' 6" long. Can anyone come up with a good reason for this?

* Update (Sept 12): I was re-reading the manual the other day and in the specifications section it states that the meter calibration cable is 1' long. Hmmmm. It also says the Receiver charging cable is 6' 6" long. Apparently they are recycling the charging cable for meter calibration.

Wish list: Persistent out-of-range alerts

Sometimes I get a high threshold alert while sleeping and I fall back asleep without treating it. When I do this, the high blood sugar can persist for hours, unless the reading drops below the high threshold and then climbs up again, triggering another alert. In other words, you only get the alert at the moment when the trend crosses out of range. You do not get repeated alerts if the reading stays out of range (there is one exception to this that I will discuss below). This is similar to using an alarm clock without a snooze option. Even if you normally get up with the alarm, occasionally you turn it off and don't remember doing so, then you sleep in and bad things might happen as a result. For instance, here is a snippet of the early A.M. on August 12:



At about 1:45 am, the reading crossed out of range and triggered an alarm. I can't remember exactly why I didn't deal with it at the time, but the high blood sugar persisted, without any more alerts, until approximately 5:45 am, when I woke up, realized I was (still) high, corrected with insulin, and brought my level back down. I don't know for sure, but I suspect other Dexcom Seven users will experience this same phenomenon. The only way I have found to avoid it is to wake up with the first alert, correct as needed, then move the threshold so I will get another alert if the readings keep trending in the wrong direction. This is a plain old pain in the behind at night.

As of now, I am starting my Dexcom Seven wish list, and here is Wish #1: I would like a snooze option with the Dexcom. I would call it a "persistent out-of-range alert". There is already one such alert built in - if the reading is consistently less than 40 mg/dL the receiver buzzes you at regular intervals until you get over 40 - but I would like to have optional extra out-of-range alerts. In my perfect Dexcom world, these alerts would occur at regular intervals specified by the user (15 minutes, 30 minutes, or 60 minutes?) to indicate that glucose values have stayed out of range. This would be helpful in lots of situations, but especially at night, when I accidentally turned off my alarm and I'm "sleeping in".

Wanna see my dawn phenomenon?

The dawn phenomenon (anyone have a better link for this?) is a powerful beast. One of my reasons for wanting a CGMS was that I was waking up high in the morning, and because of my hypoglycemia unawareness I often didn't know if the high fasting sugars were due to the dawn phenomenon or rebound from a nighttime low.

In July I posted a very nice example of the latter, when I stupidly ignored the Dexcom warning that my blood sugar was dropping, tanked into the 40's, and rebounded.

This morning, I woke up to a high threshold alert (> 140 mg/dL) at about 4:30 am. I fell back asleep (whoops), but I woke up again about an hour later and the receiver showed my blood glucose a little over 200 mg/dL.


The Dexcom Seven manual says never to correct for high or low blood glucose without a confirmatory finger stick. Most people with half a brain* will, over time, learn when they do and don't need the finger stick. I know that when my sugar is trending up, I can usually correct for a high blood sugar based only on the Dexcom reading. So I corrected, my sugar came down, and I didn't hang out for hours with excessive glucose in my blood. Hurray for Comrade Dex. Anyway, I just thought I'd post this so you can see what the Dexcom Seven does for people who wake up high. It is helping me catch nighttime lows, and it is helping me realize right away when I need to ratchet up my early a.m. basal rates.



*This footnote is to acknowledge that some Dexcom users, with whole and functioning brains, will find that they do need finger sticks to confirm every Dexcom reading before making a correction.

Back and damp in Minneapolis

A few people have written to remind me that I haven't posted for a month. Sorry about that. We were couch hopping in Seattle and it got too hard to keep up with personal computer-ing, so I gave up. We're back in Minneapolis and it has rained for a week, a week in which we also had no power due to a windstorm that took out our power lines the day before we came home. Everything is turned on now, the dehumidifier is running, and my computer is plugged in. Now I just need the housecleaning elves to show up while I'm asleep.

I have been using the Dexcom for almost two months now, and I feel like I'm just getting the hang of it. For those of you who are considering a CGMS, the learning curve can be long! This can be frustrating, especially when you're in the middle of making mistakes and trying to figure out why it's not working perfectly.

I have lots of notes from the past month for posting topics, so check back soon. Please email me or leave a comment if there is anything you want to know that I haven't covered. For now, I'll put up the latest chart showing total days that each of my six sensors has lasted. I am now on sensor 7. Note that for the 2 and 4 day sensors, especially, my inexperience might have had just a wee bit to do with their short and very expensive lives.

Stupid User Experience: Rebound high

About a week ago I had a Stupid User Experience (SUE). See the screenshot of the Glucose Trend graph. Note that this is an example of enlarging a selected time frame for closer scrutiny.

I was especially exhausted this night, and I had gone to bed without bringing some source of sugar for a nighttime low, like I usually do.

A little before 11:00 pm, I got the buzz alerting me to a breach of the low threshold. I was tired and really didn't want to get out of bed to find some juice. I'm embarassed to admit it, but all I did was turn off my basal delivery for an hour and a half, hoping that would counter the insulin on board, and I would magically sleep through the night without going low. Well, you can see the result. Around 1:30 am, I got the buzz telling me I was headed up. I think the high peaked at about 240.

Why am I sharing this? Two points. One, this is a great example of the Dexcom doing its job. One of my motivations for buying this thing was the increasing number of mornings I woke up over 200. Without this monitor, I probably would have slept through the whole rollercoaster ride. I would have gone low without realizing it, and I would have rebounded without realizing it, waking up hours later with a high blood sugar and no idea what had happened. Without the high threshold I would not have taken a correction insulin dose at 1:30, and might have peaked even higher, certainly for much longer, before I woke up.

Dexcom also did its job alerting me in plenty of time to avoid the low in the first place, which brings me to the second point. One big problem about diabetes that is probably common to many chronic conditions: it's easy to get complacent, and having the CGMS doesn't magically protect me from extreme blood sugar swings. I feel silly needing these occasional reminders, these SUEs, that simply being alerted to a low isn't enough - I still have to be in charge, even when I'm too tired. I don't know if non-diabetics can understand, and I hope I'm not the only one out there who does things like this.

I also hope after posting this that no one shows up at my door and revokes my license to practice intensive insulin management. Turning off my basal delivery - what was I thinking? Next thing you know it will be Regular and NPH for me, just like in the dark ages. Nooooooo!

The main point is: thanks Comrade Dex for doing what you're supposed to. I dropped the ball. Nice textbook example of a rebound hyperglycemia though.

Sensor 3 down the tubes

Four days? FOUR DAYS? Yes folks, sensor 3 lasted a measly four days before biting the dust. I was in denial most of yesterday, but finally last night I couldn't pretend any more. I tried to restart it, but no dice. Well, for $15 per day sensor 3 was not worth the expense. I haven't started sensor 4 yet. Probably this evening. Funny how 10 days disappointed me for sensor 1. Now I'll be thrilled with 10 days for sensor 4.

I know of one person who is on day 12 of his first Dexcom Seven sensor and still going strong. Lucky guy.