Minimally invasive technology for continuous glucose monitoring

Blood sugar management is particularly critical in the neonatal intensive care unit where the incidence of hypoglycemia is high and patients run the risk of brain damage. The staff at most hospitals obtain glucose levels in infants by drawing blood from the heel, which is a cause for recurrent pain. Some infants undergo this procedure every 1–3hours for up to a few months. Our goal is to design a minimally invasive device that allows for real-time glucose monitoring in very low birth weight infants in the neonatal intensive care unit (NICU). This glucose monitor will reduce the amount of pain and physiological stress on the infants, decrease the risk of hypoglycemia in neonates and reduce the workload on hospital staff. There is currently much room for emerging technologies in this market as it trends towards less pain and faster responses. The device should only slightly hinder the infant’s motion, be as painless as possible, and all materials used in contact with the body need to be biologically inert and cause no irritation or allergic reaction. The device will utilize a microneedle array to extract interstitial fluid and draw it through a hydrophilic polyurethane membrane and into a polarimetry chamber. Circularly polarized light will be passed through the chamber and the differential absorbance of left and right polarized light will be used to calculate the glucose concentration. A literature and patent review showed that each separate portion could be used in an effective device for minimally invasive, continuous glucose monitoring.

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Delays in Minimally Invasive Continuous Glucose Monitoring Devices: A Review of Current Technology

Journal of Diabetes Science and Technology ◽

10.1177/193229680900300528 ◽

2009 ◽

Vol 3 (5) ◽

pp. 1207-1214 ◽

Cited By ~ 110

Author(s):

D. Barry Keenan ◽

John J. Mastrototaro ◽

Gayane Voskanyan ◽

Garry M. Steil

Keyword(s):

Blood Glucose ◽

Minimally Invasive ◽

Continuous Glucose Monitoring ◽

Ex Vivo ◽

Time Lag ◽

Glucose Monitoring ◽

Time Lags ◽

Continuous Glucose Monitor ◽

Continuous Glucose Monitors

Through the use of enzymatic sensors—inserted subcutaneously in the abdomen or ex vivo by means of microdialysis fluid extraction—real-time minimally invasive continuous glucose monitoring (CGM) devices estimate blood glucose by measuring a patient's interstitial fluid (ISF) glucose concentration. Signals acquired from the interstitial space are subsequently calibrated with capillary blood glucose samples, a method that has raised certain questions regarding the effects of physiological time lags and of the duration of processing delays built into these devices. The time delay between a blood glucose reading and the value displayed by a continuous glucose monitor consists of the sum of the time lag between ISF and plasma glucose, in addition to the inherent electrochemical sensor delay due to the reaction process and any front-end signal-processing delays required to produce smooth traces. Presented is a review of commercially available, minimally invasive continuous glucose monitors with manufacturer-reported device delays. The data acquisition process for the Medtronic MiniMed (Northridge, CA) continuous glucose monitoring system—CGMS® Gold—and the Guardian® RT monitor is described with associated delays incurred for each processing step. Filter responses for each algorithm are examined using in vitro hypoglycemic and hyperglycemic clamps, as well as with an analysis of fast glucose excursions from a typical meal response. Results demonstrate that the digital filters used by each algorithm do not cause adverse effects to fast physiologic glucose excursions, although nonphysiologic signal characteristics can produce greater delays.

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