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. 2008 Jan;2(1):158-63.
doi: 10.1177/193229680800200125.

Peculiarities of the continuous glucose monitoring data stream and their impact on developing closed-loop control technology

Boris Kovatchev  1 , William Clarke
Affiliations

Peculiarities of the continuous glucose monitoring data stream and their impact on developing closed-loop control technology

Boris Kovatchev et al. J Diabetes Sci Technol. 2008 Jan.

Abstract

Therapeutic advances in type 1 diabetes (T1DM) are currently focused on developing a closed-loop control system using a continuous glucose monitor (CGM), subcutaneous insulin delivery, and a control algorithm. Because a CGM assesses blood glucose indirectly (and therefore often inaccurately), it limits the effectiveness of the controller. In order to improve the quality of CGM data, a series of analyses are suggested. These analyses evaluate and compensate for CGM errors, assess risks associated with glucose variability, predict glucose fluctuation, and forecast hypo- and hyperglycemia. These analyses are illustrated with data collected using the MiniMed CGMS® (Medtronic, Northridge, CA) and Freestyle Navigator(™) (Abbott Diabetes Care, Alameda, CA). It is important to remember that traditional statistics do not work with CGM data because consecutive CGM readings are highly interdependent.

Keywords: CGM; continuous glucose monitoring; hypoglycemia; prediction methods; time series.

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Figures

Figure 1.
Figure 1.
CGMS error during hypoglycemic clamp decomposed into error of calibration and physiologic deviation caused by blood-to-interstitial time lag.
Figure 2.
Figure 2.
CGM data in glucose vs risk space: converting data equalizes numerically the hypoglycemic and hyperglycemic ranges and suppresses the variance in the safe euglycemic range.
Figure 3.
Figure 3.
Real-time prediction of glucose fluctuation using an autoregression algorithm.
Figure 4.
Figure 4.
Autocorrelation of continuous monitoring data: the autocorrelation coefficients become insignificant at a time lag of approximately 1 hour; thus CGM readings more than 1 hour apart could be considered linearly independent.
See this image and copyright information in PMC

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