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Navigating Lows and Highs

By David Mendosa

Last Update: February 5, 2005

Meters that continuously plot the course of your blood glucose promise much greater control over your levels. Detecting when you are going hypo is just one benefit, but it offers to most immediate reward.

Controlling hypos and hypers.

Anyone who uses insulin or one of the sulfonylureas is liable to experience low blood glucose. These hypos are particularly dangerous to anyone who suffers from hypoglycemic unawareness.

Eighteen companies have announced that they have developed or are working on continuous-sensing meters. I link them all on my “Blood Glucose Meters” page at mendosa.com/meters.htm.

Two of these companies, Medtronic Diabetes in Northridge, California, and Cygnus Inc. in Redwood City, California, already have continuous meters on the market. But the MiniMed device, the CGMS System Gold, requires trips to a physician’s office to find out what your levels were. The Cygnus device, the GlucoWatch G2 Biographer, at first stirred up a storm of interest. But the GlucoWatch in practice has serious limitations in terms of cost, ease of use, and skin irritation.

Worse, the Diabetes Research in Children Network (DirecNet) Study Group, concluded that neither of these meters reliably detects hypoglycemia. The report is in the March 2004 issue of Diabetes Care and online.

Soon, however, a continuous-sensing meter that overcomes these limitations may be available. The FreeStyle Navigator Continuous Glucose Monitor is coming. TheraSense Inc. in Alameda, California, submitted a Premarket Approval Application (PMA) to the US Food and Drug Administration in late 2003. Meanwhile, Abbott Laboratories in Abbott Park, Illinois, purchased TheraSense to complement its MediSense meter business.

Abbott is asking the FDA to approve the device as a replacement for a blood glucose meter, something never done before. The MiniMed and Cygnus devices require regular calibration with separate meters.

Neil Henry, the senior product manager for the Navigator, tells me that there is more good news. “We hope that the daily costs will be comparable to those of patients testing six times a day.”

TheraSense designed the Navigator to be minimally invasive. It will use a disposable, miniaturized electrochemical sensor that the user can easily insert under the skin of the abdomen, upper arm, or elsewhere with a spring-loaded insertion device. The sensor is inserted 5 to 6 millimeters at a 90-degree angle and measures interstitial fluid. It wirelessly transmits to a device that you will be able to carry in your pocket, your purse, or leave on the bed stand at night.

The company’s published papers show variation from capillary blood of between 5 and 12 minutes. But this is not an issue because there is new data every minute.

The Navigator is designed to help us detect hypos even while sleeping, but it will also warn us of dangerous high levels. Just as important is the trends that it will detect, helping us to correlate what we eat, how we exercise, and the amount and timing of insulin or oral medication with blood glucose levels.

Unless the Navigator will be both precise and accurate, none of this information would be reliable. But it will use the same “Wired Enzyme” technology that makes the TheraSense FreeStyle and FreeStyle Flash meters among the most precise and accurate. The Navigator won’t abolish hypos and hypers, but it certainly promises to help them.

Sidebar: Welcome Back, Sleep Sentry
Another way to be aware of hypos is by monitoring its typical symptoms, perspiration and a drop in skin temperature. The Sleep Sentry, which you can wear like a wrist watch, sets off an alarm when it detects either or both of these symptoms.

“When the alarm sounds, users should always test their blood glucose to determine whether they are having a hypo,” says Marv Meier, president and CEO, Diabetes Sentry Products in Bellingham, Washington. “It doesn’t cause any irritation or discomfort when you use it, so people are more apt to use it routinely.”

The Sleep Sentry sells for $389. There are no on-going costs to run it other than changing the batteries every six months or so. The website is diabetessentry.com.  


This article originally appeared in Diabetes Health, February 2005, page 66.

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