Better Care of Diabetics, and Less Pain
nytimes.com
One day soon, perhaps as soon as a few years, many diabetics may forever
throw away the lancets they use to prick their fingers for blood sugar tests
and the needles they use to inject themselves with insulin.
Instead, they may be wearing bracelets
or even earrings smart enough to sense
and report glucose levels continuously
to an artificial pancreas: a surgically
embedded pump that dispenses just the
right amount of insulin into their
bloodstreams.
Recent inventions, as well as refinements
of older ones, have made such a
prosthetic pancreas, once a distant
dream, more and more plausible,
researchers say.
"What we are seeing this year is more
information to the diabetic patient
delivered in a less painful manner," said
Dr. Mark A. Arnold, a professor of
chemistry at the University of Iowa, who
is developing a noninvasive blood
glucose detector. "We haven't closed
the loop yet -- we don't have an
automatic system that both detects
blood sugar levels and signals a pump to
add the right amount of insulin -- but we
are getting there."
An artificial pancreas that successfully
mimics a natural one must combine a
continuous, real-time measurement of
glucose levels with an insulin reservoir
that instantly responds to these
measurements, dispensing the correct
amount of insulin just as the natural
pancreas does.
The pancreas does other things besides
dispensing insulin, the hormone that
keeps the quantity of sugar dissolved in
blood at a constant level. But research
has focused on that function because of
the growing prevalence of diabetes.
There are nearly 16 million diabetics in
the United States.
Of these about one million have juvenile,
or Type 1, diabetes, in which they
produce no insulin; the others --
adult-onset, or Type 2, diabetics --
produce insulin but tend to have a
condition called insulin resistance, in
which their bodies cannot use it
properly. This second type of diabetes
has been rising at an alarming rate in
recent years.
Diabetics who can maintain normal or
close-to-normal levels of blood sugar, or glucose, reduce the risk of grave
complications like amputation, blindness, nerve damage, heart disease and kidney
failure. A continuous glucose sensor, even one that is not yet connected to an
automatic insulin dispenser, might help to reduce these risks. It might also be a
valuable alarm clock when blood sugar drops. When that happens, people
sometimes lose consciousness.
Doctors who work with diabetics have been watching the progress toward an
artificial pancreas with growing interest. "Right now we are doing pancreatic
transplants that are fairly successful, but would like to replace these with a
machine," said Dr. George L. Siegel, a clinical endocrinologist who practices in
Manhattan.
"The idea of an artificial pancreas is marvelous."
Dr. Siegel pointed out that the technology still had many challenges to overcome.
"We have one arm of it, the insulin pump," he said.
"When a reliable, miniaturized sensor is in place to monitor glucose constantly, the
artificial pancreas will be far closer to reality."
One example of the new generation of glucose sensors looks a lot like a
wristwatch. Developed by researchers at Cygnus Inc. in Redwood City, Calif., the
monitor slips on the wrist and then uses a tiny electrical current to pull a bit of
fluid through the skin to gel pads that measure glucose levels three times an hour.
"The current is very low; all you feel when you slip on the device is a mild sort of
tingle that soon goes away," said Dr. Russell O. Potts, vice president of research
at Cygnus and senior author of a paper reporting on the monitor, which appeared
in The Journal of the American Medical Association on Nov. 17.
Cygnus has submitted its monitor to the Food and Drug Administration for
approval; a panel considering the device is expected to give its recommendation
this month.
Another continuous glucose monitor has already been approved by the agency
for use by doctors. This monitor, sold by Mini Med Inc. of Sylmar, Calif., has a
sensor that the doctor inserts, usually just below the skin of the abdomen. A wire
from the sensor goes to a small computer that can be clipped to a belt loop. The
monitor reads glucose values every five minutes for 72 hours.
Like the Cygnus device, the MiniMed sensor measures the glucose in tissue rather
than in blood and then extrapolates from this measurement. "We hope to add
hypo- and hyperglycemic alarms to the system to let patients know when their
blood sugar levels are too high or too low," said Robert Murtfeldt, director of
business development for MiniMed. He expects the next phase of the monitor to
be a consumer version in which continuous glucose readings are transmitted
wirelessly.
Dr.
Arnold, at the University of Iowa, is taking a different approach. He and a
collaborator, Dr. Gary W. Small, a chemist at Ohio University, are working to build
a noninvasive sensor. They shine a beam of near-infrared light through tissue
packed with small blood vessels -- an earlobe, a fingertip, the webbing between the
thumb and forefinger, or even the tongue.
The scientists extrapolate from the data to get the concentration of glucose in
tissue.
If the artificial pancreas becomes a reality, it will be partly because of an inventor,
Dr. Robert E. Fischell, who did the original work in the field nearly 20 years ago. In
1980, Dr. Fischell, then at Johns Hopkins University's Applied Physics Laboratory,
invented and supervised the development of a programmable, implantable pump
that administered a steady flow of insulin to patients night and day.
"By now it has been put in about 1,000 people," said Dr. Fischell, who now works
out of his home in Dayton, Md.
With Dr. Fischell's pump, implanted in the abdomen just beneath the skin, patients
measure their blood sugar regularly during the day and use the measurements to
adjust the flow of insulin. He is not involved in the monitoring research, but says
he is delighted to see it happening. An implanted glucose monitor, he said, would
finally close the loop, doing all the blood-stabilizing work that is now done by a
normal pancreas.
"Closing the loop automatically," he went on, "will be a major, major breakthrough
for the diabetic. At last." |
