Making the Most of Continuous
Glucose Monitoring
Gary Scheiner MS, CDE
Owner & Clinical Director
Integrated Diabetes Services LLC
Wynnewood, PA
“Dean”
Type-1 University
www.type1university.com
Making the Most
of Continuous Glucose Monitoring
1. What Information Is Available
2. How to Use Immediate Data
3. How to Use Intermediate Data
4. What Can Be Learned from
Retrospective Analysis
5. Optimizing CGM System Performance
Report Options:
Medtronic Carelink Personal
Sensor Daily
Overlay
Sensor
Overlay By
Meal
3
Report Options:
Medtronic Carelink Personal
Daily Summary
Layered Report:
•
Sensor tracing &
BG entries
•
•
Basal & bolus
delivery
Carbohydrate,
exercise &
logbook entries
4
Report Options:
Medtronic Carelink Personal
Statistical Summary
•
Avg, SD, Hi/Low
• # Hi/Low
Excursions, AUC
•
% Time above,
below, within
target range
5
Report Options:
DexCom DM3*
Hourly Stats
w/data table for
each hour
Glucose Trend
Includes event
entries
6
* Dexcom 7+ System not FDA approved for use in children under age 18 in the U.S.
Report Options:
DexCom DM3
BG Distribution
% high, low, normal
for each segment of
the day
Modal Day
Customizable
date range
7
Report Options:
DexCom DM3
16 Jan - 15 Apr 10
16 Apr - 15 Jul 10
Change
0.0 %
191
65
0.0 %
164
64
N/A
-14 %
-2 %
% in Hypoglycemia (39-55 mg/dL)
% in Low (55-70 mg/dL)
% in Target (70-160 mg/dL)
% in High (160-240 mg/dL)
% in Hyperglycemia (240-401
mg/dL)
0
1
33
46
1
3
48
36
N/A
200 %
45 %
-22 %
20
12
-40 %
Days Sensor Used
22
91
314 %
A1c %
Mean Glucose
Standard Deviation
Success
Report
Changes in control:
week-to-week,
month-to-month, or
quarter-to-quarter
Breakdown
by hour, with
averages
16 Jan - 15 Apr 10
16 Apr - 15 Jul 10
12 am
206
165
1 am
199
167
2 am
204
170
3 am
208
168
4 am
206
163
5 am
198
156
6 am
179
148
7 am
169
147
8 am
166
152
9 am 10 am
172
181
164
175
11 am
196
176
8
Report Options:
Freestyle Navigator/Copilot
Modal Day Report
Customizable by date
range, day of week
Glucose Line Report
Stats Report
Broken down by
phase of the day 9
Report Options:
Freestyle Navigator/Copilot
Logbook Report
(Sensor BG q10 minutes)
10
What Do We Get in Real Time?
 Trends
 Alerts
 Numbers
Decision-Making
Based on Trend Information
• Self-Care Choices
o
o
o
o
To snack?
To check again soon?
To exercise?
To adjust insulin?
• Key Situations
o
o
o
o
Driving
Sports
Tests
Bedtime
Bolus Adjustment
Based on Trend Information
• BG Stable:
Usual Bolus Dose
• BG Rising Gradually:
 bolus slightly*
• BG Rising Sharply:
  bolus modestly**
• BG Dropping Gradually:
 bolus slightly*
• BG Dropping Sharply:
  bolus modestly**
* Enough to offset 25 mg/dl
(1.5 mmol/l)
** Enough to offset 50 mg/dl
(3 mmol/l)
Immediate Info:
Hypoglycemia Alerts
• Predictive Hypo Alert or
Hypo Alert & recovering:
Subtle Treatment
• 50% of usual carbs
• Med-High G.I. food
• Hypo Alert & Dropping:
Aggressive Treatment
• Full or increased carbs
• High G.I. food
vs
Types of Alerts
• Hi/Low Alert:
Cross specified high or
low thresholds
• Predictive Alert: Anticipated crossing of
high or low thresholds
• Rate of Change: Rapid rise or fall
The Value of Alerts:
Minimizing the DURATION and
MAGNITUDE of BG Excursions
CGM Turns Mountains into Molehills
Uniform Response is Key!
1. Fingerstick
2. Act on the
Fingerstick
Setting Alerts
• Hi/Low alert thresholds are not BG target
ranges
• Balance need for alerts against “nuisance
factor”
• Predictive alerts lose value the further the
advance warning (keep below 10 min)
• Rate of FALL alerts helpful for long-term
hypo prevention (>3 mg/dl/min) (.17)
Initial Hi/Low Alert Settings
LOW:
80 mg/dl (4.5 mmol)
(90/5+ if hypo unaware)
HIGH:
300 mg/dL (18 mmol)
(lower progressively toward 180/10)
NOT RECOMMENDED: Low 70 (4)
NOT RECOMMENDED: High 140 (8)
Special Alert Settings
• Young children (higher, wider range)
• Hypoglycemia unawareness, highrisk professions (higher hypo setting)
• Pregnancy (lower, narrower range)
• HbA1c of 11.0% (higher initially)
The Numbers:
Ballpark Estimates
+/- 20% if >80 (4.4)
+/- 20 mg/dl if <80 (+/- 1 mmol/l if < 4.4)
Can The Numbers Be Trusted?
• Not during first 1-2 cycles of using the system
• Not during the first 12-24 hrs after sensor
insertion
• If BG Stable
• If Recent calibrations in-line
• If No recent alarms
Specific Insights to Derive
(a purely retrospective journey)
CGM Data Analysis Tools
Hardware/Software
• Medtronic:
– Internet Access to Carelink
– Carelink USB Adapter
• Dexcom*:
– PC, DM3 Software
– Connector Cable
• Color Printer
* Dexcom 7+ System not FDA approved for use in children under age 18 in the U.S.
Before You Analyze, Qualify.
• Were sufficient calibrations performed?
• Did the calibrations match the CGM data
reasonably well?
• Was the data mostly continuous?
• Was the time/date set correctly?
26
Before You Analyze, Qualify.
MAD = 28%
gaps & inaccuracy
27
Abnormal Artifact
Objectives-Based Analysis
1. Are bolus amounts appropriate?
– Meal doses
– Correction doses
2. How long do boluses work?
3. What is the magnitude of postprandial
spikes?
4. Is basal insulin holding BG steady?
Objectives-Based Analysis
5. Are asymptomatic lows occurring?
– Are there rebounds from lows?
– Are lows being over/under treated?
6. How does exercise affect BG?
– Immediate
– Delayed effects
7. Is amylin/GLP-1 doing the job?
Objectives-Based Analysis
8. How do various lifestyle events
affect BG?
–
–
–
–
–
–
–
Hi-Fat meals
Unusual foods
Stress
Illness
Work/School
Sex
Alcohol
Reports to Focus on
• Summary Statistics
• Modal Day / Overlay Graphs
• Individual Day Details
31
These Are a Few of
My Favorite
Stats…
 Mean (avg) glucose
 % Of Time Above, Below, Within Target
Range
 Standard Deviation
 # Of High & Low Excursions Per Week 32
Case Examples
(the “retrospective journey”)
Case Study 1:
The “Dark Side of the Moon”
•
•
Type 2; using glargine and metformin
Fasting readings OK; HbA1c elevated
Glucose (mg/dL)
400
300
200
100
0
3 AM
6 AM
9 AM
12 PM
3 PM
6 PM
9 PM
BG rising & staying high after meals.
Consider meglitinide, exenatide, mealtime bolus insulin
Case Study 2a:
Fine-Tuning Meal/Correction Boluses
•
34-y.o. pump user
Glucose (mg/dL)
400
300
200
100
0
3 AM
Breakfast and
lunch doses
may be too low
6 AM
9 AM
12 PM
3 PM
Dinner dose
appears OK
6 PM
9 PM
Night-snack
dose clearly
insufficient
Case Study 2b:
Fine-Tuning Meal/Correction Boluses
• 5-year-old on MDI; levemir BID.
Dropping low 2-3 hours after dinner.
Consider decreasing dinner bolus.
Case Study 2c:
Fine-Tuning Meal/Correction Boluses
Teenager on a pump; stays up late.
BG Rising 9pm-1am.
Consider structured night snacks with
increased bolus amount.
Case Study 2d:
Fine-Tuning Meal/Correction Boluses
•
Pumper, dropping low after correcting for highs
during the night
Corr.
Bolus

Consider increasing nighttime correction factor /
insulin sensitivity
Case Study 3a:
Postprandial Analysis
Young adult on MDI.
HbA1c are higher than expected based on SMBG
Tired and lethargic after meals
400
Glucose (mg/dL)
•
•
•
300
Meal
200
100
Meal
Meal
Meal
Significant postprandial spikes (300s).
Consider pramlintide before meals.
Case Study 3b:
Postprandial Analysis
•
•
Pump user, usually bolusing right before eating.
Potatoes w/dinner most nights.
Spiking primarily after dinner.
Consider lower g.i. food or pre-bolusing.
Case Study 3c:
Postprandial Analysis
•
•
Pump user, 6 months pregnant
Pre-bolusing (15-20 min) at most meals.
Spiking primarily after breakfast.
Consider “splitting” breakfast or walking post-bkfst.
Case Study 4a:
Basal Insulin Regulation
•
•
Pump user, 6 months pregnant
Generally not eating (or bolusing) after 8pm.
BG rising 1am-6am.
Consider raising basal insulin 12am-5am.
Case Study 4b:
Basal Insulin Regulation
Type 1 diabetes; using insulin glargine & MDI
History of morning lows
Snacking at night and not “covering” w/bolus
400
Glucose (mg/dL)
•
•
•
300
200
100
0
3 AM
6 AM
9 AM
12 PM
3 PM
6 PM
9 PM
Basal dose is likely too high. Consider reducing.
Case Study 4c:
Basal Insulin Regulation
•
Pump user, frequent lows before breakfast and
dinner.
Glucose (mg/dL)
400
300
200
100
0
BG dropping after bolus action completed. Consider
reducing basal rates early morning & late afternoon.
Case Study 5:
Determination of Insulin Action Curve
12am
3-Hour
Duration
3am
6am
4-Hour
Duration
5-Hour
Duration
Case Study 6:
Detection of Silent Hypoglycemia
•
•
Type1 college student; on pump
Frequent fasting highs (9-10 AM). Wanted to raise
overnight basal rates.
Dropping & rebounding during the night.
Consider decreasing basal in early part of night.
Case Study 7:
Effectiveness of Pramlintide/Exenatide
•
15 mcg pramlintide
•
60 mcg pramlintide
Case Study 8:
Response Curve to Different Food Types
Cereal
Oatmeal
Yogurt
Postprandial peak:
cereal > oatmeal > yogurt
Case Study 9:
Immediate Responses to Unusual Events
•
•
Type 1 diabetes;
pump user
40 years old;
athletic
Handsome,
excellent speaker
•
Late for meeting
•
Gets flat tire; eats
15g carbs to prepare
for tire change
•
Spare is flat too!!
400
300
Glucose (mg/dL)
•
200
100
0
9 AM 12 PM 3 PM 6 PM
9 PM
STRESS CAN RAISE BLOOD GLUCOSE… A LOT!!!
Case Study 10a:
Delayed Effects
•
•
•
•
Pump user
Basal rates confirmed overnight
“yellow” night: light cardio workout prior evening
“Red” night: Lifting & cardio workout prior evening
Experiencing delayed-onset hypoglycemia from
heavy workouts. Consider temp basal reduction.
Case Study 10b:
Delayed Effects
•
•
Pump user
Normal fasting readings during the week, but high on
weekends
Saturday Nights,
Dinner Out
Delayed rise from high-fat meals.
Consider using temp basal increase.
Your Turn!
• What conclusions might you draw?
• What recommendations would you give?
Your Turn!
• What conclusions might you draw?
• What recommendations would you give?
Optimizing CGM
System Performance
• Calibration
• Sensor & Site Care
• Signal reception
• Ingredients for success
Optimal Calibration
• Calibrate at times when blood glucose
(BG) is stable (fasting, pre-meals)*
• Avoid calibrations during times of rapid
glucose change*
– Post meal
– UP or DOWN arrows are displayed
– In the period following a correction with food or
insulin
– During exercise
* Not required w/Dexcom system
Calibration
• Calibrate before bedtime to avoid alarms
during the night
• Use good SMBG technique
–
–
–
–
Proper coding
Clean hands
Sufficient blood sample
Fresh strips
• USE FINGERSTICKS
• Enter the calibration immediately after
the fingerstick (Dexcom, Medtronic systems)
The Sensors
• Storage
– Refrigeration preferred (but not required)
– OK to use 1-2 months past expiration
• Site Selection
– “Fleshy” areas
– At least 2” Away from insulin infusion
– Avoid tight clothing areas, scars, bruises, lipoatrophy
– Rotate sites
The Sensors
• Timing
– Allow adequate “wetting” time (Medtronic)
– Put sensor in the night before connecting the
transmitter (Medtronic)
• Bleeding/Irritation
– Slight bleeding OK
– Profuse bleeding: remove
– Remove introducer needle at proper angle
The Sensors
• Adhesive
– Completely cover the Transmitter & Sensor
(Navigator & Medtronic systems)
– Check sensor daily for loose tape
– Apply extra tape over sensor & transmitter if tape
patch begins to “curl” around edges
• Site Irritation
– Watch for redness, swelling, tenderness
– Remove sensor with prolonged irritation (>1 hour)
Signal Reception
• Heed transmitter ranges
– Medtronic: 6 ft.
– Dexcom: 5 ft.
– Navigator: 10 ft.
• Signals do not travel well through water
– Wear receiver on same side of body as sensor
• Keep receiver very close while charging
(Dexcom)
• Charge transmitter fully every 6 days
(Medtronic)
Ingredients For Success
• Have the right expectations
• Wear the CGM at least 90% of the time
• Look at the monitor 10-20 times per day
• Do not over-react to the data; take IOB into
account
• Adjust your therapy based on trends/patterns
• Calibrate appropriately
• Minimize “nuisance” alarms
Questions?