A Glimpse Into the Future: Continuous Monitoring of Glucose With a Microfiber

Twenty-four-hour continuous glucose monitoring can provide extremely useful information about an individual’s blood-glucose pattern and fluctuations during the day and night.

Recently, Medtronic/MiniMed developed its continuous glucose monitoring system. Cygnus has also developed the GlucoWatch Biographer, which monitors glucose levels every 20 minutes and contains a hypoglycemia alarm. Both systems monitor glucose levels from the interstitial fluid under the skin.

Now a group of Italian researchers is offering a glimpse into the future of continuous glucose monitoring, with a product called the GlucoDay. According to Alberto Maran, MD, of the University of Padova in Padova, Italy, this device-which is the first system to measure glucose using a microfiber-will set a new standard for continuous monitoring.

A Thin Microfiber

The GlucoDay, according to research published by Maran and colleagues in the February 2002 issue of Diabetes Care, demonstrated “high reliability and reported values similar to finger-stick [blood-glucose] samples.”

The monitor is composed of a thin microfiber that is inserted via a removable needle beneath the skin and connected to a small portable unit (2.95 inches wide, 4.33 inches long and 0.98 inches deep). The microfiber, which is assembled by Medica of Medulla, Italy, uses 2 centimeters of hollow fiber glued to a nylon tube. The fiber is sterilized and inserted underneath the skin in the area of the navel, using an 18-gauge Teflon catheter as a guide.

Maran told DIABETES HEALTH that glucose in interstitial fluid just beneath the skin is collected in this microfiber. The insertion is performed only by a professional (a doctor or a nurse) and cannot be managed directly by the patient.

“The microfiber that is placed under the skin has a diameter like a hair,” says Maran. “No local anesthesia was used for the insertion of the microfiber.”

Maran says the GlucoDay starts measuring glucose immediately after insertion. The system takes a glucose measurement every second and stores an average value every 3 minutes-for a total of 480 measurements per day. Glucose data can then be observed continuously through an infrared communicating port and downloaded onto a personal computer.’

“Thus, individual glucose profiles can be observed over a 24-hour continuous monitoring period,” write the researchers in Diabetes Care.

Maran adds that “a single point calibration [to a capillary blood-glucose] sample has to be performed two hours after insertion for 48-hour continuous glucose monitoring.”

Glucose Levels Correlate With Fingerstick Samples

Maran and colleagues conducted a multi-center study involving 60 people with type 1 or type 2 diabetes.

Average glucose was determined every 3 minutes, and results were stored. During the 24-hour time frame, researchers also collected nine blood samples: one hour after the morning insertion; before lunch; one, two and three hours after lunch; before dinner; two hours after dinner; at 3 a.m. and at 7 a.m. the next morning. The subjects followed their usual patterns of food intake, insulin injections, drug therapy, and physical activity.

The researchers discovered interstitial-fluid glucose levels measured beneath the skin correlated well with fingerstick blood-glucose sample measurements.

Because of the GlucoDay system’s ability to communicate with a computer through an infrared port, online glucose variations can be detected even at a patient’s bedside in real time.

“Moreover, when values fell in the low hypoglycemic range [less than 68 mg/dl], the system was extremely sensitive in identifying clinical hypoglycemia,” the researchers observed. “This aspect is important for the detection of unrecognized hypoglycemia, particularly during the night, when the patient is sleeping.”

I Don’t Feel Your Pain

At the end of the study, the research subjects were asked to complete a questionnaire in which they ranked discomfort and pain during the monitoring period.

“All research subjects that were enrolled and participated in the study described only no or minimum discomfort,” says Maran.

Maran notes that plans to conduct studies in the United States using the GlucoDay have not yet been discussed. n

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