With the Medtronic sensor (and probably others), I've been told that, after inserting the sensor, that I should give it about 15 minutes to "wet" before connecting the transmitter. What is the point of this? It has a two-hour "warm-up" period anyway. Why is the initial state of the sensor so important?
And following with this logic, I, like many others, insert the sensor at night, connect the transmitter immediately, then "start new sensor" (on the pump) in the morning. This way, it's "marinated" (as some like to say), and I'm not awaken in the middle of the night for the first re-calibration. It's sitting there, connected, for hours. Is there a need to wait before connecting the transmitter? Does it really make a difference?
I don't know Scott. Kinda like buying firewood. Have to let it season a few months to dry out, but just the opposite with the sensors.
I've been using MM sensors for over 2 years now. I've never heard this and never done it. 2+ years ago, I was told 2 minutes, mostly to make sure there is no blood at the site. Now they say 3 minutes. I've never had any trouble not doing it, so not going to start now.
My guess is insertion of the sensor traumatizes the tissue, so the sensor won't generate accurate readings until the area settles down. I know sometimes my sensor accuracy improves for up to 24 hours later and maybe this is why.
(I use Dexcom.)
I will let mine "set" long enough to charge the sensor back up when I change them out...and it has always worked fine for me. Don't know specifically how long that takes but I say like u it has a "warming up" period anyway. So hey if you are getting good results, keep it up.
I have also been told that the sensor must wet for 15 minutes before connecting the MM sensor. I just use that time to charge the sensor. The MM sensor works by a gel or substance that is on the probe that sits in the interstitial fluid. Through "trade secrets" glucose will create a measurable reaction when it comes in contact with the probe. The sensor transmits the number of reactions to the pump and the more reactions the higher the ISIG value and the higher your BG is. Conversely, the less reactions the lower your ISIG value and the lower your BG is. This helps explain why sensors expire after some time and need to be calibrated. As the gel/substance on the probe gets used up there are less measurable reactions with glucose for the same BG value. When enough of the gel/substance on the probe is used up, then the sensor will no longer accurately function.
I have also noticed a few things that may help. In the last month I have been using barely expired sensors (don't tell Minimed). After the 2 hour calibration, my ISIG values much lower than they are usually for that BG. A few hours later my ISIG values jump dramatically even though my BG is staying stable. I then recalibrate the sensor a few times and all is well enough (and I even got 6 days out of the last one).
This has made me consider a few things about "wetting and warm-up". I think there could be a preservative/protectant on the probe to keep the gel/substance stable during shipment. This preservative may need to be removed by the body before the gel works correctly? Also the gel/substance may need the warm-up period to start reading (getting reliable ISIG)effectively?
I prefer to start up the new sensor as early as I can to get a good consistent flow of data, too. I would suggest that you try less of a wetting time and see what happens. You will not break the sensor, but make sure your new sensor earns your "trust" before you rely to heavily on it.
That's some good insight into how the sensor works, Capin. Does the gel get used up faster when BG (interstitial glucose) levels are higher or more erratic? I feel like that might be the case at times.
It still doesn't explain the 15 minute wait though, being that the first calibration value isn't being taken for two hours. In general, I tend to rip out the sensor when I've given up on its accuracy (whatever time of day that might be), then put a new sensor in at night and calibrate in the morning.
I have no idea if the gel is used up faster in some instances than in others, I could not even guess.
You may want to try inserting a new sensor when you get home from work if you want to try and get the new sensor active faster. I insert a new sensor after I get home from work (say 6 pm). It will ask for the first calibration around 8 pm and I can calibrate again before I go to bed at 11 pm. I like this method because I have my sensor going overnight in case I go hypo and it gives me more data to look over. But every new sensor must "earn my trust" before I rely on it.
I have to wait about 4 minutes or my transmitter won't work
This may be my imagination, but it seems to me that the transmitter won't transmit unless the sensor is adequately wet. As in no flashing light. But it doesn't usually take 15 minutes to get there; more like 5 or so. Then, when it does start transmitting, the ISIG values vary widely, and the 2 hours are for it to settle down.
And it also seems to me that quality control varies widely too -- I've had some sensors last 6 days, and others poop out after 2 days, regardless of their expiration dates. The darn things are so expensive, I'd REALLY like longer life out of them!
This could be the case.. it's about getting the transmitter to talk to the pump, not to get it to measure accurately. So-- plug the transmitter in right away and wait an hour to "Start new Sensor".... it won't delay the start any...
As for Quality Control, you're right on the money with that one. They vary WIDELY. I kind of wish Unomedical manufactured them (like the infusion sets) instead of Medtronic. Everything is wrong with the Softsensor: the soft plastic-bag packaging does little to protect the needle and sensor, the product is shipped too close to the expiration date, and the point of the needle is tapered the wrong way. And that's only what I can see with my own eyes as a consumer. I have no idea how the manufacturing/QC plant operates.