The present study investigated the relationship between blood and subcutaneous interstitial fluid (ISF) glucose by employing an amperometric glucose sensor specifically developed for 3-day continuous glucose monitoring. The apparent sensor sensitivity and ISF glucose equilibration delay were estimated on separate days during hyperglycemic clamps in four dogs in which insulin was either suppressed with somatostatin, allowed to change, or increased with an exogenous infusion. A 2-h sensor “settling-in” period was allowed before the clamps. During insulin deficiency, the sensor sensitivity and ISF glucose delay were 0.23 ± 0.03 nA per mg/dl and 4.4 ± 0.8 min. Sensitivity was not affected by increases in endogenous (0.30 ± 0.04 vs. 0.28 ± 0.04 nA per mg/dl) or exogenous insulin (0.18 ± 0.01 vs. 0.16 ± 0.01 nA per mg/dl) nor was the delay (3.3 ± 1.2 vs. 5.7 ± 1.1 and 9.2 ± 2.6 vs. 12.3 ± 1.7 min; P > 0.05 for all). Sensor glucose accurately predicted plasma glucose without correcting for delays <10 min ( r > 0.9 for all), whereas for longer delays a digital corrective filter was used ( r = 0.91 with filter). We conclude that the relationship between blood and ISF glucose is not affected by insulin and that delays in ISF glucose equilibration can be corrected with digital filters.

A1C reduction was no different between the two groups. Subjects in the CG group had increased hypoglycemia AUC and number of events during blinded CGM use; however, there was no increase in hypoglycemia AUC or number of events in the SG group. Subjects with greater sensor utilization showed a greater improvement in A1C levels.

No abstract

These results demonstrate the agreement of the CGMS to blood glucose meter values, under conditions of home use, in patients selected by their physicians as candidates for continuous monitoring. The detailed glucose information provided by the CGMS should make successful management of diabetes more easily achieved.

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.