Real-Time Continuous Glucose Monitoring: From Application to Evaluation

Transcription

1 Real-Time Continuous Glucose Monitoring: From Application to Evaluation Gary Scheiner MS, CDE Owner/Director, Integrated Diabetes Services 333 E. Lancaster Ave., Suite 24 Wynnewood, PA 1996 (877) Why CGM? HbA1c levels still fall far short of target in the majority of patients Quality of life must be taken into account Severe hypoglycemia remains a major risk for insulin users Acute hyperglycemia has an impact on emotions, mental and intellectual abilities, and physical performance Proven Need 3 children wearing a CGM device for 3 months* Average Hours Each Day Glucose Threshold Above Threshold 1. mmol mmol mmol mmol.9 Proven Need 3 children wearing a CGM device for 3 months* Glucose Threshold Average Minutes Each Day Below Threshold 3.9 mmol mmol mmol mmol 5 Fox L, et al. Presented at: American Diabetes Association 66th Scientific Sessions; June 9-13, 6; Washington, DC. Abstract 391-P. *Average HbA1c of 6.8%. Fox L, et al. Presented at: American Diabetes Association 66th Scientific Sessions; June 9-13, 6; Washington, DC. Abstract 391-P. *Average HbA1c of 6.8%. How It Works How It Works Glucose sensor is inserted in subcutaneous tissue and connected to a transmitter Glucose sensor sends minute electrical signals to the transmitter Transmitter sends data wirelessly to a pump or handheld monitor, where data can be viewed and acted upon in real-time SC Sensor Transmitter Pump or Handheld Monitor Glucose Oxidase enzyme Oxygen utilized in reaction Peroxide produced in reaction Glucose + O 2 H 2 O 2 + Gluconic Acid H 2 O 2 2H + + O e - Sensor Signal

2 How It Works System Performance Sensors generally last 5-14 days* Warm-up period after insertion; calibration Accuracy Clarke error grid: 98%+ in zones A & B (low risk of accidental insulin overdose) Mean absolute difference (real-time CGM vs SMBG): 15% CGM Options FDA Approved GlucoWatch G2 Biographer 1 CGMS System Gold 2 MiniMed Paradigm REAL-Time Insulin Pump and Continuous Glucose Monitoring System 2 Guardian REAL-Time Continuous Glucose Monitoring System 2 DexCom STS 3 DexCom STS-7 3 Medtronic ipro Recorder Freestyle Navigator 4 * Off-label information 1) Cygnus/Animas/J&J; 2) Medtronic/MiniMed; 3) DexCom; 4) Abbott. System Options System Options MiniMed Paradigm REAL-Time Insulin Pump and Continuous Glucose Monitoring System* Guardian REAL-Time Continuous Glucose Monitoring System* Medtronic ipro CGM Recorder * Body not included. MiniMed Paradigm & Guardian REAL-Time CGM Systems On-Screen Reports 3-hr and 24-hr graphs (pump); 3 / 6 / 12 / 24-hr graphs (guardian) Can scroll back for specific data points direction indicators Updates every 5 minutes Sensor change/restart after 3 days 2-3 calibrations/day Medtronic Paradigm & Guardian REAL-Time CGM Systems Real Time and Retrospective Pros Cons Predictive Alerts (Guardian) Relatively Short sensor life 3, 6, 12 & 24-hr graphs, plus datapoint history on screen Transmitter must be charged Customizable alerts, Predictive alerts (Guardian) Expensive to replace transmitters Uploadable to Carelink web site for analysis Cannot use Link Meter when sensor is used No need for extra monitor (if using Alarms may go unnoticed latest pump) Memory chip in transmitter stores data when monitor out of range Worst accuracy of available systems

3 MiniMed Paradigm & Guardian REAL-Time CGM Systems CareLink Personal: 12 Report Options Pump settings Insulin delivery Blood glucose data Sensor glucose data Carbohydrate & log book entries Can sort by time frame PDF reports can be viewed online, saved, printed, and ed MiniMed Paradigm & Guardian REAL-Time CGM Systems CareLink Personal: Key Reports Sensor daily overlay Sensor overlay by meal MiniMed Paradigm & Guardian REAL-Time CGM Systems CareLink Personal: Key Reports Daily summaries & layered reports, including Sensor tracing Basal & bolus delivery Carbohydrate & logbook entries System Options DexCom 7 STS 2-hour warmup 1, 3, 9-hr graphs Updates every 5 minutes Sensor change (or restart) after 7 days 2-3 calibrations/day Real Time and Retrospective DexCom 7 STS DexCom 7 STS Reports Pros Cons Longest-lasting sensors Limited customization Self-adhering sensors; strong adhesive Lowest start-up cost Cumbersome calibration process (older systems) 1-hr, 3-hr, and 9-hr graphs only Hourly Stats Glucose Trend Company willing to replace lost parts, nonproductive sensors Cursory analysis software Very loud alarm Very loud alarm Limited insurance support Acetaminophin Effect

4 Reports BG Distribution DexCom 7 STS Trend Analysis Freestyle Navigator Real Time and Retrospective 2 / 4 / 6 / 12/ 24-hr graphs Predictive alarms direction indicators Updates every minute Sensor change/restart after 5 days <1 calibration/day Freestyle Navigator Real Time and Retrospective Pros Best accuracy of RT systems BG meter built into monitor Detailed on-screen data analysis Extensive customization options, predictive alerts Fewest calibrations required Aggressive insurance dept. Widest transmitter range Cons 1-hr warm-up period Large transmitter Costliest system & sensors Must calibrate w/freestyle meter Drawbacks & Limitations to Real-Time CGM Cost of monitors, transmitters & sensors False alarms Inaccuracy (encapsulation tissue, lag time) False sense of security (false negatives) Pincushion effect, Extra equipment User maintenance Plasma (V1) Interstitial Fluid and Lag Time (V2) Capillary glucose must diffuse into the interstitial fluid (ISF) ISF glucose levels may lag capillary levels by 5 15 minutes When glucose levels are stable, ISF glucose levels and capillary blood glucose levels are similar Encapsulation Tissue Anything implanted in the body becomes covered with a protein / collagen layer Encapsulation tissue chemically isolates foreign objects, which may be perceived as harmful This chemical isolation decreases the sensitivity and longevity of electrochemical sensors Illustration adapted from Rebrin K, et al. Am J Physiol. 1992;277:E561 E571.

5 Practical Benefits of Real-Time CGM Rumble strips (avoid serious extremes) Peace of mind Basal & bolus fine tuning Postprandial analysis Insulin action curve determination Short-term Forecasting Learning tool & immediate feedback Eliminates some blood glucose checks??? Proven Benefit Reduction in HbA1c with CGM CGM vs. SMBG for 3 months Both groups received intensive treatment 1.2% Adjustments to therapy were made as required CGM HbA1c: % Reduction From Baseline at 3 Months.6% SMBG Chase HP, et al. Pediatrics. 1;17: Proven Benefit GuardControl Study 162 children (n = 81) and adults (n = 81) with elevated HbA1c using pumps or MDI Randomized to continuous use of a CGM device, use 3 days biweekly, or no use (control) No differences in insulin usage Deiss D, et al. Diabetes Care. 6;29: HbA1c (%) * Control Biweekly Continuous Month MDI = multiple daily injections. *P =.8 vs control; P =.3 vs control Proven Benefit Reduction in hypoglycemic excursions Duration of Hypoglycemic Excursions (minutes per event) 64.4 Alert Group Bode B, et al. Diabetes Technol Ther. 4;6: Alerts On Period 1 Period Alerts Off Control Group How to Look at the Information Immediate Intermediate Retrospective Immediate Info: Alarms Alarms are designed to alert the patient to interstitial glucose levels that have crossed specified thresholds, either high or low They may be vibrating or audible

6 Setting Alarms Alarms should be individually set Alarm thresholds are not targets Alarms should be set so they balance the need to alert the patient without becoming a nuisance Starting Alert Setting Recommendation LOW: HIGH: 4.5 mmol 13 mmol NOT RECOMMENDED: Low 4 mmol NOT RECOMMENDED: High 8 mmol Special Alarm Settings Hypoglycemic unawareness Pregnancy HbA1c of 11.% Safety Value Prediction/Forecasting Immediate Info: Real-Time Data Replace Fingersticks? After 1 st hrs BG Stable Recent calibrations in-line No recent system alarms Immediate Info: Directional Bolus Adjustment BG Stable: Usual Dose BG Rising Slowly: bolus 1% BG Rising Quickly: bolus 2% BG Dropping Slowly: bolus 1% BG Dropping Quickly: bolus 2% Use of 2/3/4 Hr Graphs Food Effects Bolus Effectiveness Pramlintide/Exenatide Influence Exercise Effects Impact of Stress

7 Use of 9 / 12 / 24 Hr Graphs Facilitates decision-making for basal insulin doses Shows delayed effects of exercise, stress, high-fat foods Reveals overnight patterns Comparison of school/work vs off days Specific Insights to Derive (a purely retrospective journey) Case Study 1a: Effectiveness of Current Program Type 1 diabetes; using insulin glargine & MDI Overnight readings are OK; HbA1c levels are elevated 4 Case Study 1b: Effectiveness of Current Program Type 2 diabetes; taking metformin Fasting BG levels generally near 1 mg/dl AM 6 AM 9 AM 12 PM 3 PM 6 PM 9 PM Meal doses insufficient; not covering snacks? 3 AM 6 AM 9 AM 12 PM 3 PM 6 PM 9 PM Daytime medication, diet & exercise education needed 4 1 Case Study 2a: Basal Insulin Regulation 3 AM 9 AM 3 PM 9 PM 3 AM 9 AM 3 PM 9 PM Stable 12 AM 4 AM, then dropping pre-dawn Dropping late afternoon 4 1 Rising 2 AM 8 AM Case Study 2b: Basal Insulin Regulation Type 1 diabetes; using insulin glargine & MDI History of morning lows Now not covering highs at night AM 6 AM 9 AM 12 PM 3 PM 6 PM 9 PM BG dropping overnight; insulin dose too high

8 Case Study 3: Detection of Silent Hypoglycemia Type1 diabetes; on pump Frequent fasting highs (9 AM) Case Study 4: Determination of Insulin Action Curve AM 6 AM 9 AM 12 PM 3 PM 6 PM 9 PM Somogyi effect during the night 3-Hour Duration 4-Hour Duration 5-Hour Duration 4 1 Case Study 5: Fine-Tuning Meal Boluses Breakfast and lunch doses may be too low 3 AM 6 AM 9 AM 12 PM 3 PM 6 PM 9 PM Dinner dose appears OK Night-snack dose clearly insufficient Case Study 6: Fine-Tuning Correction Boluses Dropping low after correcting for highs at bedtime and wake-up time AM 6 AM 9 AM 12 PM 3 PM 6 PM 9 PM Need to change correction factor & insulin sensitivity during AM hours Case Study 7: Postprandial Analysis Pre-meal BG levels are usually in target range HbA1c are higher than expected based on SMBG Tired and lethargic after meals Case Study 8: Impact of Physical Activity Type 1 diabetes; pump user Basal rates confirmed overnight Exercises in the evening (9 PM) 4 1 Meal Meal Meal Meal Significant postprandial spikes (s) 4 Exercise 1 3 PM 6 PM 9 PM 12 AM 3 AM 6 AM 9 AM 12 PM Experiencing delayed-onset hypoglycemia

9 Type 1 diabetes; pump user 4 years old; athletic Handsome, excellent speaker Late for meeting Gets flat tire; eats 15g carbs to prepare for tire change Spare is flat too!! Case Study 9: Impact of Stress 4 1 STRESS RAISES BLOOD GLUCOSE!!! 9 AM 12 PM 3 PM 6 PM 9 PM Case Study 1: Impact of Various Food Types Pasta Meal Stir-Fry Over Rice BG peaks later with pasta than rice Cereal Oatmeal Yogurt Postprandial peak: cereal > oatmeal > yogurt Real Time in Real Life Calibration Site care Ingredients for success Training, expectations, and reimbursement Optimal Calibration: Avoiding Calibration Errors Calibrate at times when blood glucose (BG) is stable (fasting, pre-meal, bedtime) Avoid calibrations during times of rapid glucose change Post meal UP or DOWN arrows are displayed on the pump screen In the period following a correction with food or insulin During exercise Calibrate before bedtime to avoid meter alarms during the night Use good technique when performing BG fingersticks for calibration. Be sure of your meter. Enter the calibration immediately after the fingerstick Sensor Sites Site Selection Bleeding/Irritation Adhesive Infection rate Patient Success Factors From Early Clinical Experience Patients who did well Wore it 9% of the time Were experienced insulin pump therapy patients Looked at it 1 to 2 times per day and did not overreact to the data Made changes (with the help of the healthcare team) by looking at trends and patterns If available, used the bolus calculator Patients who did not improve as much Did not wear the glucose sensor >5% of the time Did not trust the readings Were frustrated with nuisance alarms Source: Dr. Bruce Bode, personal observation.

10 Financial Insurance letters; building a case Appeal, Appeal, Appeal Out-of-pocket costs Use billing code 9525 To CGM or Not to CGM: The Deciding Factor Benefits > Drawbacks???