blood monitors

Starting A Continuous Glucose Monitor: Guardian REAL-Time, DexCom, Byetta

David Mendosa Health Guide July 29, 2007
  • Expertise and extensive experience have an important place in information about diabetes. But first impressions count too. The experts can miss key experiences when they aren’t coming fresh to a topic.

    Today I am coming to you fresh from my initial experience with actually using a continuous glucose monitor. I started to wear it on Friday afternoon after two superb technicians from Medtronic MiniMed trained me for more than two hours in its use. Since then, the device tells me every five minutes what my blood glucose level is.

    Continuous meters actually measure interstitial fluid, not blood glucose, but they run close together. Interstitial fluid lags about a quarter of an hour after rapid changes in blood glucose levels for two reasons. One is the body’s natural lag, and the other is the slight lag that measuring it introduces.


    That’s why I didn’t throw away my old blood glucose meters. When the continuous meter reports that our levels are too low or too high, we need to double-check with a fingerstick. We also need to calibrate the continuous meter two to three times per day to get it to give us more and more accurate readings. However, in exchange for these two or three fingersticks, we get 288 blood sugar values per day.

    The continuous glucose monitor that I’m using is the Guardian REAL-Time.

    It wasn’t my only choice, but I picked it because it’s the most advanced one available. This is Medtronic MiniMed’s second generation device, replacing the Guardian RT (which confusingly stood for real time too). This new device also pairs with the company’s Paradigm pump, the world’s only system to integrate an insulin pump with real-time continuous glucose monitoring.

    DexCom makes the other continuous choice, which I also like a lot. So much, in fact, that I have owned stock in that company since even before the Food and Drug Administration approved that monitor. But I don’t have any conflict of interest to disclose in writing about my new Medtronic MiniMed device.

    Most people use continuous monitors to bring down their A1C level. But my A1C level is already where I want it to be. I want to reduce my glycemic variability, the measure of the quality of the A1C, as Dr. Irl Hirsch calls it.

     

    I want to be able to see variations in my levels overnight, in the morning for the dawn phenomenon, after big meals, and before and after strenuous exercise. So yesterday, when I began to be able to see my levels at five-minute intervals, was an exciting day for me.

    With the continuing help of Byetta, I am still eating small meals, so I haven’t yet noticed mealtime spikes. This weekend I am relaxing after four days of strenuous hikes in Rocky Mountain National Park last week, so I can’t report yet on the effects of exercise. I don’t seem to have the dawn phenomenon any more.

    But I got some surprises. For the so-called “happy hour” yesterday before dinner I “rewarded” myself with a 1.5 ounce shot of my favorite single-malt Scotch whisky. I know that alcohol on an empty stomach reduces glucose levels, but I didn’t know by how much or when. It was a small amount, but I felt what I thought was being tipsy. In fact, it was probably feeling low.


  • My new Guardian REAL-Time told me that my level dropped from 112 to 74. The surprise was how long it took to drop, almost two hours.

    We have known for years that alcohol on an empty stomach is one of the few things that can reduce our glucose levels. I wrote about those things along with two others in my first book, The New Glucose Revolution: What Makes My Blood Glucose Go Up...And Down? (New York: Marlowe & Co., second American edition in July 2006, and other publishers in the U.K., Australia, and Taiwan). But I know now that because of the long time that alcohol takes to work, it’s not a useful tool.


    I have only one useful tool to bring down my level when it gets out of hand. That’s exercise. I remember from years ago when my wife’s blood glucose level went up to about 200. When we took a brisk walk for just five or 10 minutes, her level dropped quite a bit.

    Since I don’t take insulin, one of the Medtronic MiniMed technicians emphasized that when my levels go too high, exercise is the only thing that I can do right away. But a big benefit of the Guardian REAL-Time is that I can avoid peaks the next time because of the knowledge the system gives me.

    On the other hand, when my glucose level gets too low, as it did after drinking Scotch yesterday evening, the thing to do was obvious – eat dinner. My level wasn’t so low that I needed to use glucose tabs.

    Another surprise is how complex continuous glucose monitors are compared with traditional blood glucose meters. Those meters have just four components – the meter itself, test strips, a lancing device, and lancets. We now have systems that integrate the meter and the strips and others that integrate lancing device and lancets. Soon, we will have one from Pelikan Technologies that will integrate all four parts.

    But continuous glucose meters have a surprising number of parts, including the monitor, the sensor, the transmitter, the insertion device, and the software and its cables. I haven't even looked at the software yet.

    I wear the monitor, which looks like a small cell phone, on my belt, and sometimes I carry my cell phone, my iPod, and my pedometer there too. I’m thinking of getting a GPS for my hikes as well. Maybe the next iPhone will combine all of these devices.

    The monitor needs to be within six feet of the sensor, which I wear to the side of my stomach. I don’t need to carry the monitor all the time, and when it’s not within range, the sensor keeps sensing.

    The sensor and the transmitter that I am wearing sure are small, much smaller than what people who used Medtronic MiniMed’s first continuous glucose monitor got. What I wear looks like a tiny Bandaid with a little bulge in the middle. Already I am seldom conscious of wearing it.

    I hardly felt it when I inserted it with the needle in the insertion device. I don’t have a needle in my body now – it’s a flexible plastic tube under the sensor. The sensor is waterproof enough that I was able to leave it on for my showers.


  • Since I have never used insulin, I don’t have any experience with insulin pumps. I asked the Medtronic MiniMed technicians whether pumps or continuous glucose monitors were more complex. They told me that continuous glucose monitors take more training.


    They gave me excellent training, and the support that Medtronic MiniMed is giving me is first rate. One of the technicians even called me on Saturday to see how I am doing. I did have some questions that I asked her, but I sure am doing fine with this new device that gives me the further knowledge I need to control my diabetes.