Continuous Glucose Sensing

Glucose monitoring systems thatcontinuously plot the course of bloodglucose promise much greater control overblood glucose levels. Detecting when youare going low is just one benefit, but it is themost immediate reward.

Eighteen companies have announced thatthey have developed or are working oncontinuous-sensing meters.

Medtronic MiniMed already has continuousglucose-monitoring systems on the market,but currently they require users to visit adoctor’s office to learn what their levels were.

Soon, another continuous-sensing systemmay be available—the FreeStyle FreeStyleNavigator Continuous Glucose Monitor.

TheraSense, Inc., in Alameda, California,submitted a pre-market approvalapplication (PMA) to the U.S. Food and DrugAdministration in late 2003. Meanwhile,Abbott Laboratories in Abbott Park, Illinois,purchased TheraSense to complement itsMediSense glucose meter business. Theresulting company, Abbott Diabetes Care, isheadquartered in Alameda.

Abbott has asked the FDA to approve thedevice as a replacement for a blood glucosemeter, something never done before. Othersystems have been approved only as asecondary source of glucose information,and it was still necessary to continue using atraditional glucose meter.

The FreeStyle Navigator will use a disposableminiaturized electrochemical sensor that theuser can easily insert under the skin of theabdomen, upper arm or elsewhere with aspring-loaded insertion device. The sensor,which measures interstitial fluid, is inserted5 to 6 millimeters below the skin and at a90-degree angle. It wirelessly transmits toa device that can be carried in a pocket orpurse and can sit on the nightstand at night.

The company’s published papers show a lag-timevariation from capillary blood glucoselevels of between 5 and 12 minutes. This isnot a problem, however, because there arenew data every minute.

The FreeStyle Navigator is designed to helpdetect a low even during sleep, but it will alsowarn users of dangerous high levels. Just asimportant are the trends that it will detect,helping users to correlate their food intake,activity levels, and the amount and timing ofinsulin or oral medication with blood glucoselevels.

The FreeStyle Navigator won’t abolish bloodglucose lows and highs, but it certainlypromises to help control them.

Welcome Back, Sleep Sentry

Another way to be aware of lows is to monitorthe typical symptoms of hypoglycemia: excessiveperspiration and a drop in skin temperature. TheSleep Sentry, worn like a wristwatch, sets offan alarm when it detects either or both of thesesymptoms. However, not everyone exhibits thesetwo symptoms that are needed to trigger thealarm.

“When the alarm sounds, users always shouldtest their blood glucose to determine whetherthey are having a hypo[glycemic episode],” saysMarv Meier, president and CEO of Diabetes SentryProducts in Bellingham, Washington. “It doesn’tcause any irritation or discomfort when you useit, so people are more apt to use it routinely.”The Sleep Sentry sells for $389. There are noongoing costs other than changing the batteriesevery six months or so. To learn more, see theWeb site at

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