Can anyone confirm that the following process will work correctly with the MM CGMS? I want to avoid the two hour ‘down time’ when switching sensors.
When the current sensor is nearing the end of its life…
1. Insert new sensor while leaving current one in
2. Wait 2+ hours
3. Remove old sensor
4. Charge transmitter
5. Attach to new sensor
6. “Start New Sensor” on the pump
If you have done this and found it to work/not work please let me know.
Thanks!
It might work. But what we found works the best is the following:
- Remove old sensor and transmitter.
- Insert new sensor and attach charged transmitter - because we then cover with tegaderm.
- Allow the sensor to sit overnight.
- Start sensor in morning, which is then ready immediately to be calibrated.
By leaving the sensor in overnight, we have reduced almost all sensor errors, my daughter is ready to head off to school in the morning with the sensor working, and only needs to be calibrated at lunch. We allow her to run “higher” that night so that we have no worries about lows during the night.
You will not be able to get readings from a new sensor until 2 hours after you’ve connected the transmitter. There’s no way to get around this 2 hour period after attaching a new sensor. The 2 hour warmup starts when the connection is made.
I don’t think that is exactly the case unless I am missing something. The transmitter does not know what sensor it is connected to (sensors don’t have unique IDs as far as I know) and when you “Start New Sensor” after the first 3 day period you get readings right away.
Are you suggesting that the transmitter knows when it has been removed from a sensor physically and that triggers the 2 hour wait? Or something else?
Thanks!
I have to disagree with this too, but only from personal experience, no technical know-how. I always do as was mentioned above:
- new sensor in night before change is due (transmitter still in old one)
- sleep with new sensor in place (covered by tape or tegaderm), old one is still giving me data
- remove transmitter from old sensor, remove old sensor, charge transmitter
- plug transmitter into new sensor
- seems to take a lot less than 2 hours to really “warm-up” and asks for a BG reading.
But again, no technical know-how, just an observation!
Very cool. Thanks for the info as this sounds exactly like what I want to do.
IMO, observation = technical know-how! You likely know more about this aspect of the CGMS than most of Medtronics’ CDEs 
Most of the time I’ve noticed my sensors take less than 2 hours (usually 1.5 hours), but even if I leave a sensor in for a few hours, I typically go through a calibration time. But I have heard from several people that sleeping overnight voids the calibration time. I’m not sure how because calibration would be for the transmitters benefit, not the sensors, so it shouldn’t matter how long the sensor is in but how long the transmitter is active for a particular sensor. Again, I have no technical know-how either. I really think in this case you’re better off asking Minimed for the answer! They should probably know and/or have heard from others how it works.
Hmmm. I think the calibration process is actually to create a ratio between your BG (via finger stick) and the interstitial fluid glucose readings from the sensor. I don’t think the transmitter cares really.
That ratio varies from sensor to sensor and over time as a sensor ages which is what creates the need to calibrate. The 2 hour start up period is to allow the new sensor time to stabilize its readings which allows, in turn, a reasonable calibration to BG.
Based on Emily’s experience and what I have read I believe the 2 hour start up process is tied (in some way I don’t exactly know yet) to the range or stability of readings from the sensor. For example, the last sensor I started gave a reading of 60 when first inserted which is way out of range. When it was 6 hours old the readings were ‘normal’ vs. BG. It could be that the pump is looking for values that are within a range and/or that are stable reading to reading to determine if it needs to wait for the two hour start up or not.
I have never had a new sensor be ready for the first reading in less than 2 hours from when I connected it to the transmitter. The transmitter is what is keeping track of the time, not the sensor.The transmitter knows when you’ve disconnected or connected from/to something. Have you ever noticed the flashing green lights on it? Those are telling you that you’ve just connected/disconnected and everything is a go. It doesn’t matter whether you’re re-connecting to the same sensor that you’ve had in for a week, if you disconnect, you’re stuck with the 2 hour warm -up period. It’s got nothing to do with how stable the ISIG values are and everything to do with the electronics and timer inside the transmitter.
And full disclosure - I’ve got a PhD in electrical engineering so I’m fairly confident I can figure out how lots of electronics work. The transmitter is dependent on a timer/countdown and nothing else.
It seems that Emily F is getting a different result as she writes
"…
- new sensor in night before change is due (transmitter still in old one)
- sleep with new sensor in place (covered by tape or tegaderm), old one is still giving me data
- remove transmitter from old sensor, remove old sensor, charge transmitter
- plug transmitter into new sensor
- seems to take a lot less than 2 hours to really “warm-up” and asks for a BG reading.
…"
Based on your description it should still take her 2 hours to start the new sensor, right? Yet, she indicates it takes much less than that.
Either way, I will try the switch next time I replace the sensor and see what happens.
2 hours from when you connect to when it will ask you for a meter reading (if you start your sensor right after connecting). If you don’t get 2 hours, you’ve got a faulty transmitter. Anybody can think that 2 hours doesn’t seem like 2 hours, but if you actually watch the clock, it’s 2 hours. There is absolutely no way to get around this.
Now, if you connect your transmitter and go about your day for a few hours, you’ll get an almost immediate “METER BG NOW” from when you start a new sensor. I find it best to do it this way b/c otherwise, I’ve got to keep the transmitter and receiver very close together for 2 hours.
It could be worse - you could have a Navigator. It has a 10 hour warm up period that you cannot get around.