Continuous Glucose Monitoring Systems

  • Michael JoubertEmail author


Actually available continuous glucose monitoring (CGM) devices typically consist of (1) a glucose sensor, subcutaneously inserted, that continuously measures interstitial glucose levels; (2) a transmitter connected (physically or wireless) to the sensor; and (3) a receiver displaying glucose data. The technology of these sensors relies on an electrochemical approach using glucose oxidase enzyme (GOx). Sensors are coated with GOx that catalyzes the oxidation of glucose to gluconolactone, producing O2, H+, and electrons. Glucose concentration is thus correlated to an electrical signal which is transduced to the transmitter. Then this signal is back translated in glucose values to be displayed on the receiver. Most systems need to be calibrated with regular capillary blood glucose values in order to properly associate glucose values to the electrical signal. Only one system requires no calibration as it is “factory calibrated” (see below). Life span of each sensor type is linked to the subcutaneous stability of GOx and its ability to catalyze glucose oxidation over time. Non-electrochemical technologies are also developed for CGM but are not currently available in routine practice (optical, impedance, piezoelectric, magnetic methods) [1]. CGM data can be displayed in real time to the patient, on a dedicated receiver or directly on the screen of an insulin pump, as a continuous biofeedback. Such CGM systems are called “real-time CGM” (rt-CGM), “therapeutic CGM,” or “personal CGM.” They are intended to be used continuously, on the long term, to improve metabolic control, thanks to real-time management of diabetes by the patient himself. CGM data can also be recorded during a limited period of time, without being made available to the patient in real time, for retrospective analysis by health-care professionals (HCP), in order to tailor the treatment according to glucose profiles (Fig. 4.1). This use of CGM is named “retrospective CGM” (retro-CGM), “diagnostic CGM,” or “professional CGM.” It’s important to notice that rt-CGM devices, although primarily designed for daily patient’s use, also store large amounts of glucose data that can be retrospectively used by HCP to analyze glucose profiles and, thus, can be used as retro-CGM.


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© Springer Nature Switzerland AG 2019

Authors and Affiliations

  1. 1.Diabetes Care UnitCaen University HospitalCaenFrance

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