1. How the Glucose Sensor Works
Continuous Glucose Monitoring

2. Objective
To learn the components of the Glucose Sensor and how the Glucose Sensor works in interstitial fluid
Key Points
Proper technique when handling and inserting the Glucose Sensor as well as ongoing care leads to a successful CGM experience
The Glucose Sensor requires calibration with a blood glucose meter

3. Glucose Sensor Components
Introducer Needle Handle
Introducer Needle
Connector to MiniLink or iPro
Sensor Electrode inside the needle
Body

4. Glucose Sensor Components
Attaches to the MiniLink Transmitter or iPro Recorder
Connector
Never hold or pick the Sensor up by the needle handle
Introducer Needle Handle
Introducer Needle
22 gauge (1/2 diameter)
Bevel faces down
Discard after insertion
Pick up the Sensor on either side of the Connector
Body
Sensor Electrode inside the needle

5. The Sensor Electrode Sits Inside the Introducer Needle
Reference electrode
Closest to the skin
Working electrode
Counter electrode
Maintaining an Optimal Sensor Placement Ensures Success

6. Layers of the Glucose Sensor
Semi Permeable Membrane
Selective to glucose and oxygen
Membrane
Enzyme
The membrane surrounds a glucose oxydase enzyme
Enzyme
Electrode
Electrode

7. Outermost Layer of the Glucose Sensor
Semi Permeable Membrane
Selective to glucose and oxygen
Membrane
Ensures biocompatibility
Maintains the required glucose to oxygen ratio required for diffusion to the enzyme layer
Functions as a glucose limiting membrane
Enzyme
Electrode

8. The Glucose Sensor Consists of 3 Layers
Semi Permeable Membrane
Selective to glucose and oxygen
Enzyme
The membrane surrounds a glucose oxydase enzyme
Electrode

9. Glucose and Oxygen Enter Membrane1
A semi permeable membrane that is very selective to glucose and oxygen
The Membrane is required for biocompatibility
In subcutaneous tissue
Glucose = 72 to 360 mg/dl
Oxygen = 0.9 mg/dl
Glucose is 5 times more prevalent in subcutaneous tissue
Membrane
Enzyme
Electrode

10. Glucose and Oxygen Enter Membrane1
Glucose and Oxygen
When the glucose and oxygen come in contact with the glucose oxidase enzyme, the first chemical reaction takes place
Membrane
Enzyme
Electrode

11. First Chemical Reaction2
Glucose and oxygen come in contact with the glucose oxidase enzyme
Glucose and oxygen are converted into Hydrogen Peroxide (H2O2) and gluconic acid
Glucose and Oxygen
Membrane
Gly Acid
H2O2
Enzyme
Electrode

12. Second Chemical Reaction3
H2O2 seeps through to the Electrode layer
A voltage is applied to the Electrode, causing H2O2 to breakdown into:
Hydrogen
Oxygen
2 electrons
Membrane
H2O2
Enzyme
2e-
Electrode
The more glucose in your body, the more H2O2 generated.
The more H2O2, the more current generated.

13. Converting ISIG to a Glucose Sensor Value
The 2 electrons generate a current called ISIG
ISIG is converted to a sensor glucose value when a BG meter value is entered into the pump or monitor for calibration
Membrane
Enzyme
2e-
Electrode
ISIG
The ISIG is Proportional to Glucose Concentration

14. Converting ISIG to a Glucose Sensor Value1 2 3
Check glucose level with a BG meter
Enter BG reading into the insulin pump or monitor
Accept BG reading as a calibration
The insulin pump or monitor calculates the calibration factor:
Cal Factor
Meter BG / ISIG
Sensors require calibration using a blood glucose meter

15. Converting ISIG to Sensor Glucose
Meter BG
ISIG
2e-
ISIG
Cal Factor = Meter BG / ISIG
108 mg/dL / 10.8 (ISIG) = 10

16. Calibration Factor Examples
Meter BG Glucose / ISIG = Cal Factor
108 mg/dL / 10.8 (ISIG) = 10 (Cal Factor)
10 (Cal Factor) x 10.8 (ISIG) = 108 mg/dL
Cal Factor x ISIG = Glucose
128
112
Example: Cal Factor = 10
ISIG
BG (mg/dL)
10.8
11.2
12.8
2e-
2e-
ISIG =
11.2
12.8
108
112
128
calibrated
00:05 min
00:10 min