Wednesday, December 29, 2010

Some CGM results and how to fix your reed switch in your wireless computer.

I've just completed my third week of using the Dexcom 7 continuous glucose meter. So far the values are mostly in the ballpark with my glucose meter. At least within 20%. Which is OK for the most part. And it is mostly continuous. As you can see below in the nighttime plot for this day sometimes when I apparently am turned one way it misses some readings.

The next two plots also confirm interesting trend that I was thinking may have been happening before I got the CGM. The first plot I went to bed with a reasonable level of 160ish. Then it jumped around a little bit and drops until morning. Most nights it stays pretty constant though. I ate breakfast and it rises and then drops until lunch. This is all good.

Now the second plot.... My sugar was a little high at bed so I took a small amount of Humalog along with the Lantus. This seems to happen even if I take the tiniest bit of Humalog at the same time I take Lantus. I have more plots that look just like this when I took Humalog.... The sugars drop and stay at a constant low level all night pretty much. Sometimes it takes a while to figure out my name when I finally wake up. And then when I eat (even a light breakfast) the glucose shoots through the roof even with extra insulin after breakfast. This plot is actually higher than my other meter read on this day but the point is still clear. Notice that it also takes a long time to drop back down.

So after looking several different nights data..... The key is to not take any Humalog with Lantus at night and try to go to bed with a level of around 150. And hope I can wake up in the morning.


OK so I got a Garmin Edge GPS cyclocomputer. It basically does everything. Tells you heartrate, cadences, speed, position, altitude, maps your ride etc etc. The weak link? OK other than leaving it in your pocket and washing it.... It worked for a month or two then died. I sent it in and they gave me a new one for a fee. They didn't tell me what killed it but probably the washing. So anyway the real flaw is shown below in the speed/cadence sensor. The speed sensor picks up a signal from a magnet attached to the spokes to give better speed data if you are in thick trees or whatever and don't have a good GPS signal.

On the little arm that pokes out and can be adjusted to get it close to the magnet on the spokes is a reed switch attached to a small circuit board. This is a cool little thing in itself and is shown below. As the magnet passes it it creates a connection and completes a circuit which then sends a signal to the computer to compute speed. A similar circuit collects cadence data.
So what happened to mine and what is the flaw. The reed switch is a glass tube filled with inert gas. So it makes sense that the last time this thing worked was just before I bumped the sensor and it got whacked by the magnet. When I took it out the glass was shattered.

So the key to opening up your GCS 10 it to take a chisel or something and carefully split it open on the seam. I left it attached to the cadence part to help stabilize it. Then I just pulled the plastic back to reveal the switch attached to small circuit board and pulled it out.

The next step is to find an old computer that broke and can be cannibalized. I had just the thing--pays to be a pack rat--on the broken one below. So I soldered the board below to my unit and slipped it in.

And here I am slipping it in. One thing I noticed was that this reed switch had a bunch of glue all over it to not only keep it stuck but I think to keep the glass from breaking as easily as it was completely encased in the plastic.

I hooked it all up. Tested it out by passing a magnet past it and the little test light on the sensor flashed green. Good to go! So I slipped it in pushed the cover over stopped working. Damn!
I thought the little circuit boards were close enough in size but this one was just a hair longer and it broke when I pushed it in. Damn! Luckily I had another old sensor that took apart. I soldered that reed switch on to the original board and tested it out. This one had some rubber between it and it's circuit board to keep it from breaking as easily.... If only Garmin would have put something in there to keep it from breaking so easily. If you look around on line or forums there a lot of these things breaking! So I put this one in and it fit nicely and all the electronics tested out. So now get out the epoxy and.... Damn epoxy has gone bad..

Time to get out the other epoxy and mix it up on the seed catalog....

Now spread the epoxy on the arm and press back together and clamp to cure. And let's see how long this fix works. By the way a new GCS10 goes for $37 with free shipping on You can also buy a reed switch here for $1.50 + SH if you didn't keep parts around.

So the moral to this story. Don't get your sensor too close to the spoke magnet and save all those old cycle computer parts when they break. And thank your spouse profusely for letting you solder and epoxy on the kitchen table.

Sunday, December 12, 2010

10 km classic ski race and Dexcom 7 CGM update. And everyone is an expert!

This morning Becky left a post on my Facebook wall. "You doing the race in CB? Give me a call." So Yeah I was thinking about it. What time did we start? I hadn't classic skied this year but had put some wax on my skis last night. I was planning on skiing somewhere today so why not? It's only 10K or 6.2mi.

This is day 3 of using a continuous glucose meter. The Dexcom 7. It takes a reading every five minutes from a electrochemical probe stuck into my belly and taped then taped on. It is pretty small and I got used to it pretty fast. You are supposed to be able to stay in water for 30 min and up to 3 ft deep. So you can take shower. It lasts for 7 days before you replace the probe that goes into the skin. The transmitter part works for 12-18mo before the battery runs down and clips into a new probe. Here I am modeling the transmitter.

And here is the receiver. You have to keep it around 5 feet from your belly to get the signal. I have to say it could some improvements. It is a bit big--especially compared to other things like my GPS that can receive signals from a HR meter, cadence, wheel (for speed when GPS is not good) and even a power meter, or a cell phone that can do a bunch of stuff as well. It has a clip that hooks it to your belt but it could be better... You can also input when you eat and how many carbs, when you exercise, if you are sick and alarms for high/low readings and for fast rate of change high or low. IT DOES NOT COME WITH AN ATTACHMENT FOR A BIKE! It is also not easy to view when you are skiing.

As you may be able to see in this picture that you can see an arrow showing a rate of change and the current reading. The readings for the most part seem to be in the ballpark of my One Touch meter. You can enter the meter readings into it to calibrate it and you have to do it at least every 12 hrs. It also has a plot of the readings of time vs blood glucose level for 1, 3, 6, 12 and 24 hrs. One thing that bugs me is that the y-axis is stuck at 400. I wish you could show it to only 250 maybe or have it auto scale. It just makes your data hard to evaluate as it is all scrunched up at the bottom. You can download it all to the computer to get a better look at it.

What have I learned from it so far? Well, at night and after dinner it is very interesting to see what my values do. They tend to be real flat and can drop to lower values than I would like. I was kind of just guessing blindly in this area before the meter. And during the day, I could check it anytime but it gives you a much better idea of what is going on. Some things that so far I knew. When I do something like a ski race or x-country or bike, my sugar drops steadily and I have to eat regularly. When I play hockey, it just starts going up and after the game it just keeps going up and up.....

So back to the ski race. It started at 10 so I went and picked Becky up at 8:45. My sugar was a bit low in the morning and when it is, after I get up my body dumps out a bunch of sugar so it gets high. So we checked into the race and got our kick wax dialed. At the beginning of the race, I was putting my receiver into my chest pocket so I could look at the changes in glucose afterwards. A guy I took a ski clinic with saw it and asked if I was texting someone. It kind of looks like a phone which is good so you don't have to explain it all the time. I said no, I'm type 1 diabetic and it's a meter. He said, "You're in good company with Kris Freeman" Kris is Type 1 Olympic skier. Another lady says, "You should really go gluten free." and she then continues to go on and on that my sugars would be much better controlled if I was gluten free. So blogs are officially where you can tell people that they are crazy if you can't get a word in edgewise during the situation.... So I never told her that i WASN'T gluten free. Which I'm not. I like bread. And she didn't know if I was type 1 or type 2. I was thinking "Oh let's take out YOUR pancreas and you can test it ALL out.... I tried to tell her that there were many variables to living without a functioning pancreas and that it would be interesting to see if gluten free was a way to go. But she cut me off and huffily said "You should really go gluten free" and skied off.

So I went back to the end of the line up of skier to grab my skis and tighten my boots and then they started the race as I was still getting I was near the back. I just passed a bunch of people and settled in behind a girl that was pretty fast and we cruised along. My skis were gliding well and the kick wax was working pretty well. The course was not really hilly and it was around 23F with just a little wind. We turned to come back and she made me lead and we made it to the finish. I was a bit tired and some muscles that hadn't been used since I skied last year were a bit sore. Not too bad. I switched to skate skis and skied for a while more and headed back to Gunni.

A good day.

Thursday, December 9, 2010

New gizmos and too much Fe?

Over the past few years I've been going to the health fairs and getting my blood drawn and tested for normal type things as it was covered by work and then getting the optional A1C. In this tiny town it is faster then going to the hospital after getting the Dr note. So a few years ago a couple of the tests starts coming back high. The iron tests. I just assumed that it was probably because I exercise a lot at high altitude or something.

In an effort to 1) get lower A1C values (better blood glucose control. It wasn't terrible but not super duper.) and 2) check out if I could improve my glucose in racing I decided to try a continuous glucose meter, or CGM. I decided that the Dexcom 7 seemed pretty good as it has the smallest transmitter and worked pretty well. These meters are not quite as accurate as the One touch meter that I use but pretty close. For example it doesn't really matter if it is really 200 and it is reading 215.... The CGM measures glucose every 5 minutes so it can show you if it is falling or rising fast or slow or on a level track--which is handy. So to get the meter I had to have the Dr clear it and while I was doing that I dropped off the old test results that I had not given them to add to the files. The PA that I know pretty well was putting the results in and talked to me about the possibility that I may have a condition called hemochromatosis. It's basically a problem where you absorb too much iron and the body has a hard time getting rid of it and after many years it causes some serious problems... One of which it diabetes. Well don't have to worry about that... But it also causes the liver among other organs to not work. The main thing you have to do is give blood pretty regularly... So he had me taking some more tests. Now as it stands I am going to see a hematologist next week and may have a milder form of hemochromatosis. Or maybe not. Anyway it's genetic so if you are related to me by blood you may want to get checked out.

Wednesday night the CGM came and I've been testing it out for the past day. So how does it work? I would have to say the sensor that goes in the belly is pretty small and not too noticeable. the receiver that picks up the signal is a bit large and doesn't come with a bike mount. It has been showing pretty accurate readings. I have to say I have been testing my sugar quite a bit to check it and looking a the meter a lot. I has shown some things that I have seen but gives some real data. I had a hockey game tonight and I have had problems where as I play and afterward my sugar will be high. And sure enough as I sit here an hour after playing it starts to go up and up. During hockey the transmitter did rub against my breezers as they come up pretty high. But not too bad. I just left my receiver on the bench. It has a five foot range and sends a signal every five minutes so as long as I stood nearby it seemed to pick up most of the time.

Well more on the meter and my possible hemochromatosis later.... Now just one more week of school and then time for some skiing.