UPDATE: THIS THREAD IS CLOSED AND NOT CURRENT. For an updated view of my experience with this product, please go to my more recent post, from 12/5/2007, on the same topic, just click this link.
First I should state that I have not yet been using the continuous glucose metering from Medtronic/MiniMed for long, less than one month. The learning curve appears to be quite large, even for someone with a strong technology background and competence with other electronic devices, even for someone already in tight glucose control.
I would also like to state that even at these early stages and with the lengthy laundry list of issues I’ve had, I have also gotten some very good information from the continuous monitoring, even at this early stage. I have already adjusted my basal rate for a much more even reading throughout the night. I have already learned that I was under-bolusing, especially for breakfast and lunch. I have also had times when the alerts have told me my blood sugar was either high or low that I would otherwise have remained unaware of.
These hint at great things to come as I learn more about the proper use of this device. I would hope that this page will serve to help others set realistic expectations for what they can get from this device and shorten their learning curves to avoid some of the pitfalls I have made. As I get better with this device, I expect to post more threads with pointers for improving results. I will be more likely to do so if others respond on this thread to let me know that it is being read.
These are the Issues I have had so far with Continuous Glucose Monitoring:
- The transmitter does not work well in a modern office. I had mine less than an index finger’s length from the pump with my cell phone on the opposite side, and even tried turning it off, and still got lost sensor. Weak signal and even lost sensor are common in my office, with wifi, cell phones, cordless headsets, blue tooth, microwave ovens, and other radio transmissions all around. I really believe that the solution is to have a wire connection option. Wireless is simply not yet reliable enough for medical devices, especially at the chosen frequency of 900 MHz.
- The tape on the sensor needs to be more like the tape on a silhouette infusion set. The front of the sensor, where the tape does not even continue all the way around, is the most critical area since the transmitter pulls away from that end.
- The relationship between interstitial glucose and blood glucose requires better research and documentation. My experience so far hints at a couple of interesting possible relationships.
- As is well documented, the rise in interstitial glucose lags the rise in blood glucose, though the time seems to vary.
- During exercise, I am starting to notice that the interstitial glucose may drop before the blood glucose, which may or may not drop as well. This seems to be the case when I do not have an unabsorbed bolus in me. If I have insulin not yet absorbed, that absorbs rapidly with exercise and drops blood sugar first.
- If blood glucose is rising and action (i.e. a bolus) is taken, the interstitial glucose will likely never reach the level of the blood glucose.
- At times, especially during extremes of inactivity such as car rides and watching movies, rises in blood glucose may never trigger rises in interstitial glucose.
- Behavior of the pump software on lost sensor produces actively worse readings. One problem with lost sensor is that the behavior of “find lost sensor” does not simply reconnect the transmitter and pump using the old calibration. As noted above, getting a time when both blood glucose and interstitial glucose are steady is difficult. When a sensor that was well calibrated is lost, the new reading, required in two hours, is likely to produce radically worse calibration than the nice early morning flat calibration it replaces. Often, this means that the device is useless for the rest of the day.
- Sensor is often lost after far fewer than 40 minutes. Sensor is treated as lost if transmitter is removed to check the battery. Both of these cause bad calibrations afterward, as noted above.
- I need to verify this one a bit better. However, my suspicion at present is that alerts generate either vibrate or beep alerts depending on the setting of the alert type at the time that the alert was set up. So, in the case of a meter BG required, it may beep when the pump was set to vibrate, because, at the time that the sensor was attached, the pump was set to beep. This is, of course, a very minor issue.
- In my experience, calibration is more accurate whenever both your interstitial glucose and blood glucose have been fairly constant for at least a half hour. Whenever this is the case, enter your meter blood glucose to avoid having to enter a less good calibration reading at a later time.
- The best calibration reading of the day is typically just before breakfast for me, always always always take the opportunity to use this calibration.
- I have my alerts set at 60 for low and 140 for high. Unless you want to know about every fluctuation, you probably want to stick with the defaults. However, if you are not getting enough alerts, consider moving the numbers closer together for tighter control.