Minimed Constant Glucose Monitor
Happy New Year! As promised a follow up to my earlier post in which I detailed my changeover to an insulin pump with constant glucose monitoring. As described on December 12, I’ve been using the Minimed Paradigm 522 with the Guardian constant glucose sensor.
If you’re completely bored by this and follow my articles of travel, restaurants, clubs, and Denver life – you should skip this and read my story on American Airlines flight 1469. However as insurance starts to cover this equipment more type 1 diabetics will be utilizing this and similar monitors – so hopefully this will help those new to this.
In brief: Pager size insulin pumps are used by type 1 diabetics in lieu of injections. Pumps better mimic the pancreas by giving a constant dose of insulin with manual doses at meals or as needed. An ancillary gadget called a “constant glucose sensor” sends your current blood sugar reading to your pump, providing you with a constant stream of blood sugar numbers and direction of blood sugar level – rather than the lone number obtained from a finger prick.
Overall it’s an incredible life changing tool for a type 1 diabetic. Knowing the TREND of your glucose is something that was only in the realm of imagination for years. Now, to be aware and know your blood sugar minute by minute, WITHOUT the need for (as many) messy finger pricks is an enormous step forward. And to have to blood glucose number sent directly to a small screen is a wonder of med-techy synergy.
Here are the drawbacks. Well not exactly drawbacks, but things to be aware of in order to develop your own workarounds and methods to match your daily life.
Appearance: The sensor and transmitter piece aren’t quite as sexy looking as the photos. It’s necessary to cover them with a small dressing. No big deal – the starter kit includes transparent adhesives. Medtronic sells a pack of 100 at the astronomical price of $62, but you can find similar at Walgreens for under $5.
New Sensor Obligation: When starting a new sensor you need to allot yourself a seven hour block of “awareness time.” Better said: keep your meter handy.
After starting a new sensor you’re required to enter your first BG in two hours, then another in five hours. It’s not practical to start a new sensor late in the evening, as you’ll be alerted to enter a BG in the middle of the night. After the two and five hour BG calibrations you’ll be prompted for one BG entry (calibration) every 12 hours. This is pretty easy, and I’m getting used to “thinking 12 hours ahead.” For example if I do a calibration at 2pm, I have to remember to do one around 10pm or before bed so my pump doesn’t wake me up at 2AM requesting a calibration. Typically morning and early evening is best, (before meals,) as your BG needs to be relatively stable for the best calibrations. You can set your calibration reminders up to four hours before a necessary BG entry. But again think 12 hours ahead. If you’re planning to sleep in Saturday morning you don’t want your last Friday entry to be 6pm, or you’ll be harassed by your pump at 6am. This hasn’t been an issue so far as I’ve actually been taking MORE manual readings to test the accuracy.
Accuracy and Rapid Changes: During periods of rapid change the CGM definitely lags. If my BG is 200 and I lower it down to 100, my spot checks show it will be a bit slower to reach 100. BUT, I do show during normal periods of minor fluctuation it’s very accurate. Its stable periods (non-rapid change) it’s been leveling out matching my finger sticks within 20 points.
However I am bit disappointed in how it matches blood sugars that are rapidly rising. And I’ve found when my level is LOW and bring it up, the readings bottom out and take quite a while to reach up to where it should be. These “flat periods” and annoyances are similar to blogger Jay’s experience in this recent post. I see way too many of these stagnant periods when I KNOW my levels are changing, but the results are slow to follow and stagnate within 10 points.
Attempting to remedy this I’m experimenting with new sensor sites. I realized my last sensor was on a site where I’ve given myself many shots over the years. I’m on day two of a new sensor, placed on my upper leg, and am watching the results closely. Pasta dinner at Maggiano’s last night DID prove more accurate, although my manual checks showed little fluctuation anyway.
Sensor Life: When you start a new sensor the pump allows a three day use, and when expired instructs you to change sensors. Like infusion sites most users extend their sensor life to reach six to nine days. The “three day use” is only the number documented by clinical testing and approved by the FDA. There’s nothing unhealthy about using a site longer provided your body, (and awareness of accuracy,) are comfortable with it.
The pump sends you a “sensor end” message after three days. It’s easy to tell the pump you’ve “replaced” the sensor by selecting “Start new sensor.” Your pump will prompt you for a BG shortly, (usually 15 minutes, and not two hours from a newly inserted one.) And remember since the pump thinks you’re on a “new” sensor you’ll be prompted for the initial five hour check. Obviously there are accuracy concerns with using a sensor repeatedly, but as you learn how your body operates with the sensor you can make adjustments for that.
The sensor doesn’t like being soaked in hot water. Showers are fine, but hot tubs and baths reduce the life of the sensor. Thus if you’re removing a sensor Friday and planning on some hot tub soaking Saturday night, best to just start a new sensor Sunday as not to waste a sensor for just one or two day’s use.
Other Sensor Messages and Other Stuff
When flying you’re supposed to remove your transmitter from the sensor, and use the “Reconnect Old Sensor” feature after landing. (Or anytime after disconnecting the sensor from the transmitter.) Yeah right. I have no plans to do this. Flying is when I WANT my CG numbers as during travel my blood sugar fluctuates more due to eating crappy (or no) food. The range is less than 10 feet and not a threat to airplane safety. Minimed only tells you to do this because they have to. On a related note I took two flights over the past week and my pump and sensor did NOT set off security.
Lost Sensor: If your pump is out of range from the sensor for more than 40 minutes you’ll get a “Lost Sensor” message. Just hit “Find Lost Sensor” and you should get readings again within 15 minutes.
Cost: Unless you can stack your closet with an unlimited supply of sensors I recommend keeping your sensor life in mind when planning certain activities. As mentioned hot tubs, jello wrestling, or other activities in which you want to be “untethered from the sensor” require some planning ahead in changing of sensors. Unlike the pump you can do without the sensor and it’s readings for as long as you need to – it’s just normal life before the CGM.
Without insurance sensors are $350 for a box of 10. That’s $35 per sensor. A “wimpy” injection of your sensor can be a $35 mistake. And time consuming as well since you’ll be annoyed by “calibration errors” until you just replace it. If your insurance covers sensors with a nominal co-pay then of course you can be more liberal in use. However remember inserting a “new” sensor still requires the two hour window to start, then your five hour calibration. So even if I could afford a new sensor every three days I’d still use them longer to avoid the the calibration requirements.
Overall – grade B Balancing my expectations with my month of experience I’d give the Guardian a B, wavering between a B+ and a C+. Each person needs to tailor their use and data according to their needs. Hopefully my experimentation with different sites will remedy my issues of “flat periods.” But keeping that in mind I still love using it. The technology WILL improve and get better, and realizing the potential it will be available to more and more people. I’ve found it addicting having the numbers at my side no matter what my activity.
If anyone is also using this or new I’d love to read your reviews. I find these almost as interesting and exciting as “How Air Traffic Control Works!” Take care and have a killer 2008!
James Van Dellen