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Navigator's poor recovery from false LOW readings.

Discussion in 'Continuous Glucose Sensing' started by zatff, Jun 16, 2009.

  1. zatff

    zatff Approved members

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    I have had several episodes when Navigator CGM readings start giving false low readings. These often happen at night but usually it recovers in a minute or two and resumes more accurate readings. But several times it continued to keep dropping and gives very low readings for hours. During these times I tested with finger sticks on Navigator and another meter and get BG levels 100-150 points higher and well in normal or safe levels. Usually these episodes end with a message to replace the sensor after a few hours. These erroneous low readings can be 10-50 % of actual finger stick readings and stay low for hours.

    I have one on now that started malfunctioning last night and gave erroneous readings for eight hours. Then it started working again and was right on with finger stick tests. When it started working again it jumped from 48 to 225 and finger stick reading at that time was 228.

    It is easy to guess that the 39 or 26 readings are bogus when finger stick readings are 100 points higher, but not so easy to know that the 123 reading is actually a 248. I find because of these reliability issues I actually test more than I did before the Navigator.

    Anyone else having this happen?
     
  2. sneakermom

    sneakermom Approved members

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    I haven't had that happen. Have you checked the transmitter to see if there is a crack in the battery case. Maybe it's an issue with the transmitter. Either that or you got a bad lot of sensors. I would definitely call tech support and let them know what's going on.
     
  3. BrendaK

    BrendaK Neonatal Diabetes Registry

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    Some people get false low readings at night if they are lying on the sensor and putting pressure on it. If you move around and roll over it will catch up in 20 minutes or so.

    We did have an issue the other night with false low readings, but that I'm sure was because I calibrated at a bad time earlier in the evening. The CGM kept alarming all night (said 55 and he was 105) so I ended up turning the low alarm off. I was quite alarmed when I woke up and it said 45 with an angled down arrow :eek:). When I checked he was actually 74.

    The other issue we've had with false lows is if the transmitter comes slightly unclicked from the sensor mount. That can cause false lows and also sensor alarms. If you check it and click it back in it will catch up fine.
     
  4. selketine

    selketine Approved members

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    We've had that issue when I think the sensor was pulling out - if the tape got loose. If that happens the sensor doesn't recover.
     
  5. timsma

    timsma Approved members

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    We're on our first week of the navigator and we had the exact same problem last night. It was in the evening though,,,,,,and thru part of the night so I know it wasn't caused by him laying on it since he was upright. It's on his abdomen. I'm feeling frustrated with it. Last night I have to say I was almost ready to give up on it thinking it isn't much better than the MM one then.......but this morning it is spot on again. Weird.
     
  6. Nancy in VA

    Nancy in VA Approved members

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    The only time we had it happen we actually had a bad sensor. And believe it or not, we were able to recover it in the morning. Other than that, our lows have been pretty spot on!
     
  7. ecs1516

    ecs1516 Approved members

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    We have had false low readings if they were laying on the sensor but it recovered within 10 minutes after rolling off the sensor. We had a sensor pull out at night and it started readings rapid drops and got to LOW. It had pulled out. It is a very small sensor and it doesn't take much for it to fall out. You must keep the tape tight around transmitter.
     
  8. Melissata

    Melissata Approved members

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    Only had that happen once in the 6 months that she has been using it. She was sleeping in a big chair and must have been putting pressure on the sensor because I put it really far back on her arm. I just made her move and it went right back up. If you don't tell it that you removed the sensor right away, you will get a low reading also, and you don't want that number in your history so it is best to tell it that you are removing the sensor when you are going to change it. If the sensor has pulled out or even partially out, then you could get the low too of course because it can't read the fluid correctly.
     
  9. Diana

    Diana Approved members

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    Well, with all the things that happened to us on the Navigator... this one never did!

    We did have a few false lows at night. The few times it happened it took at least an hour to recover - none of this 10 minutes stuff! But we never saw a sustained false low - or sustained inaccurate reading at all - for over 8 hours!

    I vote for a dislodged sensor also. Where do you have this one?
     
  10. ecs1516

    ecs1516 Approved members

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    In our eight months of using this on two kids (that is 16 months of total use), we had a lot of false lows at night where they were sleeping on it. It would alarm and I would have to go in the middle of the night and roll them off it and then wait till they come back up because Navigator has no snooze on the low alarm. We haven't had this pressure problem on the Dexcom transmitter.
     
  11. moco89

    moco89 Approved members

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    This situation kind of sounds like when the sensor gets dislodged for me. Since the length of the sensor is so short, the sensor can pop in and out of my skin when the tape stops adhering to my skin. This causes false lows all the time for me, especially in the summer.
     
  12. zatff

    zatff Approved members

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    I just got a new transmitter cause the other one had a fine crack in it and I had hoped this would end some of the problems. The sensor I mentioned above only recovered for three hours and then went back to being 100 plus points too low so I removed it. Customer support did send me a new receiver which I started today with a new sensor.

    I know the Navigator is prone to false low readings at night. I guess it has to do with reduced circulation but they usually bounce back in a few minutes. I have had sensors quit working after a day or two for unknown reasons but these sustained low readings are like it is running in a limp mode. The sensors was still properly inserted when I removed it but looked like it may have had dried blood around the probe end. I am hoping the Dexcom will work better for me since it has a longer probe inserted at an angle that should allow more service area for sensor to measure. I wonder how Navigator reading every minute instead of every five minutes influences it readings too?
     

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