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style="FONT-FAMILY: Arial; FONT-SIZE: 10pt">It's An Open Loopstyle="FONT-FAMILY: Arial; FONT-SIZE: 10pt">The MiniMed Paradigm REAL-Time that
Chris Jarvis uses is an open-loop system. It's not a closed-loop system or an
artificial pancreas, which would give him automatic feedback and inject just the
right amount of insulin at precisely the right time for him to control his blood
glucose level. Instead, Chris decides that for himself based on the monitor
reading and trend.
A closed-loop system will
have three parts. Pumps to delivery the insulin and continuous blood glucose
monitors are proven technologies. The third part is the algorithm ó computer
software ó connecting the pump and the monitor. This part is the major question
mark on the path to a closed-loop system.
style="FONT-FAMILY: Arial; FONT-SIZE: 10pt">By David Mendosa
Medtronic MiniMed is the
first company to link an insulin pump and a continuous glucose monitor. Approved
by the Food and Drug Administration in April, the pump part of the combination
is already available. The company expects the monitor part to be available by
the end of this month.
Chris Jarvis and His
But one lucky young man has
used both the pump and the continuous monitor since last summer. Chris Jarvis
lucked out because he lives in Canada, where his doctor got it released to him
in early September.
While Chris has had
diabetes since 1994 when he was 14, he's lucky because he has more experience
than almost anyone in using the new combination pump and monitor to help him
avoid highs and lows. "The big deal for me is not having the fluctuations while
I am training," Chris told me recently. He is training with the Canadian
National Rowing team, which intends to participate in the 2008 Olympic Games in
Beijing. He competed in the 2004 Olympics in Athens.
"I used to fluctuate
quickly up to 500 and 600 without realizing what was happening," he continued.
"And anything below 100 would put me in a big panic. I got so frustrated with
these highs and lows that I got turned off on testing, because I didn't
understand what I was doing wrong. Now, with all the information the monitor
gives me, I know how to make improvements and can relax."
The combined pump and
monitor that Chris uses has a long name. It's the MiniMed Paradigm REAL-Time
Insulin Pump and Continuous Glucose Monitoring System, and it includes two major
components. The first is a MiniMed Paradigm 522 or 722 insulin pump with a
built-in calculator. The second is a REAL-Time Continuous Glucose Monitoring
System, similar to Medtronic MiniMed's Guardian RT Continous Monitoring System,
which has been available in limited release since last September.
The system's alarms warn of
lows and highs. Chris sets his low alarm at 80 and his high alarm at
Trend arrows point up or
down to show the direction and rate of change in glucose. Trend graphs show the
effect of meals, exercise, insulin, and medication on blood glucose
"My continuous monitor had
an advantage over the Guardian RT, because it has graphs, which give me an easy
visual picture of what is going on in the last three hours," Chris told me. "The
24-hour graph also tells me when my highs are happening, and I can see what went
on when I'm asleep."
Chris says that in the
first few months after getting this combination he had to figure out how to use
it. "But since then I have learned so much about my diabetes and how to react to
different situations. It's all about problem solving in real