Ups and downs

So speaking of dropping; I was very impressed with the bottom end of the sensor performance of the Navigator. On the first sensor I was once in the 70s and the Navigator was on the ball, and not even late to the party. During a deep, fast drop it kept up with the frequent Presto finger sticks really well. I can’t say, at least not yet, if the sensor is actually better than Med-Ts. The Guardian does lag quite a bit on steep drops. This is partly because of the time lag between interstitial fluid and capillary glucose (true of all CGM systems) but also because of sampling lag. Guardian updates every five minutes. Under normal circumstances, that’s more than enough. But if you are dropping fast, you can go a long way in five minutes. This inherent defect in the system is brilliantly addressed using the slope and predictive alarms. Nonetheless, this seems to be the issue that pisses people off the most. Navigator, on the other hand, updates every minute, and I think that this is why she tracks so much better during a drop. I guess 240 seconds makes quite a difference.

Either way, whether by sensor design or sampling speed: Navigator more accurately reports during a steep drop. Navigator one. Guardian zero. In the same vein, Navigator more accurately reports rebound recovery following a hypo. Guardian will frequently show you continuing to drop after you’ve taken on your fifteen carbs; you could over correct with this “information.”

CAUTION: the observations above are based on one sensor only. Time, and more sensors are needed to know if this is the exception or the rule. I’ve got six more sensors in my stash, hopefully that will be enough to reveal the system’s dark side if she has one.

I also found that the Navigator was pretty much worthless above 200. The higher I got the more she lagged, sometimes by a stunning amount; and the less likely she was to be correct about change in glucose. Going up pretty rapidly, according to Guardian (confirmed by Presto finger sticks) Navigator still showed me flat and level. Guardian reports faithfully on highs. I guess I care more about lows, but I still found it odd. Now again, in fairness, I have a confession. My first Navigator sensor is an expired one. I had to scrounge what I could get. Some of the sensors are older than others. I started with one of the oldest just in case I screwed it up on the first insertion. It “expired” six months or so ago. Still, it was damn impressive on the low end. I wouldn’t want to drink milk that was six months old. So I’m curious to see if the current almost-in-date sensor will behave better in a brownie-laden environment.

Navigator also gets high points for easy insertion. On my second shot at it (pardon the pun) I found it very easy. The first time I covered the entire affair with the largest IV3000 bandage I’ve ever seen. It was the mother of all IV3000’s. This time I’m going without and hoping the tape on the sensor tray holds up OK for me.

So despite generating a significant amount of trash, the Navigator insertion is superior to Guardian. Navigator one. Guardian zero. Navigator is a much smaller diameter sensor probe, and it goes into you at a 90 degree angle. It is minimally invasive. But is it as secure? That is the possible downside for highly active folks. Guardian is a whopping 18 gauge needle.

It can be painful. The angle is 45ish degrees, and it is long. It can tag muscle tissue in lean folks, which is very painful. Having worn them for many years I can attest to the fact they are destructive enough to cause some built up of scar tissue (also true of the much smaller infusion sets). Sometimes inserting a Guardian sensor can be very painful. Other times not at all. Putting in a Navigator is pretty much the same as putting in a pump infusion set if you use one of the inserter devices. More of a pinch sensation than pain, per se.

Especially for kiddos, I think the Navigator would be better. Of course, the system takes up more skin landscape, and the receiver is bigger too….so….

One nice thing about the Navigator alarms is that they are at least decently loud. On the high setting they’d probably wake most folks up. I’d still like a higher option for heavy sleepers or winter coats. What bugs me about alarm volumes on these devices is that we can CHOOSE. So why not give us a decent number of choices? Why only Baby-bear, Momma-bear, and Poppa-bear? Someone out there wants Mouse-bear. I want T-Rex-bear.


Next time: transmitter trouble