Continuous Glucose Monitoring (CGM)
Continuous Glucose Monitoring (CGM) V. Sanoe Harrison MD Living Well With Diabetes Conference CHOP – 3/28/15 Outline • What is CGM, How does it work – Glucose is turned into an electrical signal • Why Use It? – Improved A1c or average glucose – Protection against hypoglycemia – Decreased Variability • How to Use it Outline • Limits and Challenges – Accuracy • Absolute • Time Delay – Sites and Skin – Information overload • Example/s • Q&A What is CGM • Relatively new electrochemical sensors placed under the skin (subcutaneous tissue) – MiniMed 1999 – Dexcom 2006 InterstitialFLuid Interstitial Fluid Semi‐permeable Membrane Glucose Oxidase Embedded Layer Hydrogen Peroxide Gold or other Metal Core Pieces of CGM Remote Monitoring • Dexcom Share • Medtronic MySentry • Night Scout Dexcom Share • iPhone or iPod bluetooth • Received on up to 5 devices Medtronic MySentry • Color Screen Display • Power Supply • Outpost – Transmits information from the Pump to the Monitor – Enables you to monitor from up to 50 feet away – This means that your child or loved one can be sleeping in one room while you are in another Night Scout • • • • Non FDA approved Build it yourself Costs >$100 for parts Website, Cell/Data Service • http://www.nightscout.info/ Why Use CGM? • Normal blood sugar = no complications CGM in 24 Healthy Volunteers Day Ave ± SD = 93.0 ± 7.0 mg/dl Night Ave ± SD = 81.8 ± 6.3 mg/dl Power of Continuous Sensing DCCT (Diabetes Control and Complication Trial) mg/dL 120 150 180 240 270 300 DCCT (Diabetes Control and Complication Trial) DCCT (Diabetes Control and Complication Trial) Sensor Lowers HbA1c /year Decreases Hypoglycemia How to use it – Proper calibration • Calibrate when the glucose is stable Time Delay Black: blood glucose Red: CGM glucose How to use it – Real‐time benefits • Predicting low or high sugar – Reviewing Data • Basal – Is my sugar stable overnight? • Carb Ratio – Is it working? • Sensitivity Factor – Is it working? Date 3/26/2015 4:03:00 AM 3/26/2015 8:32:00 AM Event Carbs 56 grams Insulin 2.3 units Other Examples • • • • • • Logging exercise, carbs, illness Exercise (late hypoglycemia) Over‐correction Assessing basal rates (or Lantus) Meal Assessment – ie Medtronic Pre/Post Post‐meal Dosing Minimed Patterns DEXCOM‐Patterns Hourly Stats Glucose Distribution Limits • Accuracy – Must be calibrated (at least 2 times/d) – Mean Absolute Relative Difference (MARD) • Sensors 14% • POC glucometers 5‐10% Challenges • • • • • Discomfort Won’t stay on Skin Reactions Won’t work Too many alarms Feature G4 Platinum by Dexcom MiniMed 530G with Enlite by Medtronic Diabetes Guardian® REAL‐Time by Medtronic Diabetes Sensor life 7 days 6 days 3 days Sample Frequency Every 5 minutes Every 5 minutes Every 5 minutes High/Low Alerts Yes Yes Yes Trending Arrows Yes Yes Yes Predictive Alerts No Yes Yes Insulin Delivery change based on glucose reading No Yes – Threshold Suspend feature (in response to LOW BG ) No Range of Monitor to Transmitter 20 feet 6 feet 6 feet Transmitter Waterproof Yes, depth of 8 ft for 12 hrs Yes, depth of 8 ft for 30 minutes Yes, depth of 8 ft for 30 minutes Calibration with blood Minimum every 12 hours glucose Minimum every 12 hours Minimum every 12 hours Communicates with an insulin pump YES – the Animas Vibe system Yes Yes – the MiniMed REVEL system Monitor size 4” x 1.8” * Changes with pump integration 3” x 2” Displays on insulin pump 3.2" x 2" Download Capability Dexcom Studio, Diasend Windows Web‐based Carelink Personal Mac/Windows Web‐based Carelink Personal Mac/Windows Website www.dexcom.com www.medtronicdiabetes.com www.medtronicdiabetes.com
© Copyright 2024