INTRODUCTION TO CONTINUOUS
GLUCOSE MONITORS
H. Peter Chase, MD
Professor of Pediatrics
Barbara Davis Center
Aurora, CO
Keystone Conference
Wednesday, July 16, 2008
Barbara Davis Center for Childhood Diabetes May 2008
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CGM Introduction Class
• The slides from our course for families interested in
starting CGM are available for use in your centers. They
are on our website: www.barbaradaviscenter.org. The
slides can then be accessed by any of the following
methods:
• 1. Click on the “CGM Slideset” tab
• 2. In the “Online Books and Teaching Slides” page:
http://www.uchsc.edu/misc/diabetes/books.html
• 3. In the Clinical Resources section (last entry):
http://www.uchsc.edu/misc/diabetes/school.html
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What is a CGM?
(Continuous Glucose Monitor)
• A device that provides “real-time” glucose readings and
data about trends in glucose levels
• Reads the glucose levels under the skin every 1-5
minutes (10-15 minute delay)
• Provides alarms for high and low glucose levels and
trend information
• The 3rd era in diabetes management
Barbara Davis Center for Childhood Diabetes May 2008
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Who Should Use a CGM?*
1) The person and the family must both
want a CGM
2) A youth must be willing to wear the
sensor (and carry the receiver)
3) Using good diabetes care (4 BGs/day)
4) Good support system
5) Adequate body “real estate”
6) Cost of CGM (RNs to elaborate)
*(Understanding Pumps and CGMs, p.100)
Barbara Davis Center for Childhood Diabetes May 2008
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Continuous Glucose Monitoring (CGM)
WHY?
A. Prevention of low blood sugars (alarms)
B. Prevention of high blood sugars (ketones)
C. Minimize wide glucose fluctuations
D. Behavior Modification
E. Prevention of Complications (?)
Barbara Davis Center for Childhood Diabetes May 2008
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How common are glucose levels <60mg/dl
during the night in children with T1D?
– French (i) and Australian (ii) data showed
approximately 50% of children with low BG
(<60mg/dl) during the night (on NPH bid)
– DirecNet data (one night in hospital with blood
sugars every 30 min.)
A) 2001-2002: 39 of 91 (43%) low BG
(44% of children on insulin pumps/56% on NPH)
B) 2004: 14 of 50 (28%) with low BG
(all on insulin pumps or Lantus)
Barbara Davis Center May 2008
i)
ii)
Beregszaszi M, et al. J Pediatr. 131, 27, 1997
Porter PA, et al. J. Pediatr. 13, 366, 1997
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Continuous Glucose Monitoring (CGM)
WHY?
A. Prevention of low blood sugars (alarms)
B. Prevention of high blood sugars (ketones)
C. Minimize wide glucose fluctuations
D. Behavior Modification
E. Prevention of Complications (?)
Barbara Davis Center for Childhood Diabetes May 2008
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“Snapshot of BG levels”
Barbara Davis Center for Childhood Diabetes May 2008
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Continuous Glucose Monitoring
Barbara Davis Center for Childhood Diabetes May 2008
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Hyperglycemia is common,
especially after meals
50%
40%
30%
Breakfast
Lunch
Dinner
20%
10%
0%
< 180
Barbara Davis Center May 2008
181 - 240 241 - 300
> 300
Boland et al, Diabetes Care 24:1858, 2001
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Continuous Glucose Monitoring (CGM)
WHY?
A. Prevention of low blood sugars (alarms)
B. Prevention of high blood sugars (ketones)
C. Minimize wide glucose fluctuations
D. Behavior Modification
E. Prevention of Complications?
Barbara Davis Center for Childhood Diabetes May 2008
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Three Parts to All CGMs:*
A. Sensor
B. Transmitter
C. Receiver/Monitor
*(Understanding Pumps and CGMs, p.103)
Barbara Davis Center for Childhood Diabetes May 2008
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A)Sensor
(p.103)
Barbara Davis Center for Childhood Diabetes May 2008
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B)Transmitter
(p.103)
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C)Receiver or Monitor
(p.103)
Barbara Davis Center for Childhood Diabetes May 2008
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What does “Calibration” mean and
why do I need to do it?
• Calibration is a process that gives a
fingerstick BG value to the CGM system
so the values will align with each other
• Number of Calibrations vary by device
• Best times to calibrate are when the BG
values are stable: before meals and before
bed
• Do not calibrate when arrows are present
Barbara Davis Center for Childhood Diabetes May 2008
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What type of data will we get?
1) “Real-time” (Immediate)
i. Trend graphs (p.109)*
ii. Alarms (p.110)*
iii. Trend arrows (p.113)*
Barbara Davis Center May 2008
*(Understanding Pumps and CGMs)
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i) TREND GRAPHS*
Trend graphs – Knowing a glucose
level is 240 mg/dl may not be as
important as knowing the “trend.”
*(Understanding Pumps and CGMs, p.103)
Barbara Davis Center for Childhood Diabetes May 2008
ii) ALARMS (p.109)
Can warn patients of current or
projected high and low blood sugar
• Projected alarms: 10, 20, or 30 minute warning of
impending hypo- or hyperglycemia
(Navigator and Guardian devices)
• Threshold alarms: warning when glucose is below or
above a set value (all devices)
Barbara Davis Center for Childhood Diabetes May 2008
iii) TREND ARROWS (p.110)
Rate of Change Arrows
Gives the up-to-the-minute glucose value and
a rate of change arrow
Glucose rising quickly
>2 (mg/dL)/min
Glucose going up
1 to 2 (mg/dL)/min
Fairly stable glucose
-1 to 1 (mg/dL)/min
Glucose going down
-1 to -2 (mg/dL)/min
Glucose falling quickly
>-2 (mg/dL)/min
Barbara Davis Center for Childhood Diabetes May 2008
Second type of data:
(Retrospective, must download)
2) Retrospective
A. Modal Day Graphs (p.113)
B. Pie Chart (p.114)
C.Statistics (p.113)
*(Understanding Pumps and CGMs, Chapter 17, p.109)
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A) Case Study:
Modal Day Graphs*
•
•
•
•
•
Teenager with T1D for 9.5 years
Started Navigator: Sept. 2005
Starting HbA1c: 7.1%
Most recent HbA1c: 6.0%
Current number of low BGs per week (<60
mg/dL or <3.3 mmol/L): 1/week
• Three “modal-day” graphs:
*(Understanding Pumps and CGMs, p.113)
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A) BASELINE GLUCOSE MODAL DAY:
i) Prior to Navigator Use
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A) GLUCOSE MODAL DAY
Breakfast/Lunch Improvements
ii) After three months of use
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A) GLUCOSE MODAL DAY
iii) Most recent report
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B) PIE CHARTS (p.114)
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C) STATISTICS (p.113)
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USE OF CGM RESULTS:
(To “fine-tune” insulin and diabetes management)
i) Important not to overwhelm families
*** One change at a time ***
ii) Look for patterns 2 out of 3 days
iii) A behavior modification device  Missed
boluses, snacking, low BGs on CGM
iv) Good initial communication with HCP
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Questions?
• The presentation by the nurses
will be next.
• You will then examine the CGMs
from 3 companies.
Barbara Davis Center for Childhood Diabetes May 2008
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Part 2: CLINICAL STUDIES
• Use of CGM (The Navigator) in Clinical
Studies of Children:
A) Insulin Pump Study (JPediatr
151:388,2007)
B) Lantus Study (DiabetesCare
31:525,2008)
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CGM can help with glycemic control
A) 30 Pump Patients Using Navigator x 13 weeks*
N
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Mean Age
T1D duration
11.2 yr
5.8 years
Female
40%
HbA1c
Initial
13 wks
7.1±0.6%
6.8±0.7%
(p=0.02)
*DirecNet J Pediatri 151,388,2007
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HbA1c
8.5
Baseline A1c 7.0%
Baseline A1c >7.0%
HbA1c (%)
8.0
N=15
7.5
*
N=15
N=12
N=15
7.0
N=13
6.5
N=15
N=15
§
N=13
6.0
5.5
Baseline
Week 7
Week 13
Week 26
Black dots denote mean values and boxes denote median, 25th and 75th percentiles.
* p=0.004
vs. baseline; § p=0.002 vs. wks 9-13.
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Percent in target range (71-180)
Percentage of Navigator Glucose Values
in Target Range
90%
Baseline A1c 7.0%
Baseline A1c >7.0%
80%
70%
N=11
N=15
N=13
N=13
N=15
N=11
N=13
60%
N=11
N=15
50%
N=15
N=9
N=15
N=11
N=14
40%
30%
Baseline
Wks
1-4
Wks
5-8
Wks
9-13
Wks
14-17
Wks
18-21
Wks
22-26
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Percentage of Navigator Glucose Values
Below 70 mg/dL
Percent below 70 mg/dL
14%
Baseline A1c 7.0%
Baseline A1c >7.0%
12%
10%
8%
N=13
6%
N=15
N=11
N=11
N=15
4%
N=11
N=15
N=11
N=15
2%
N=13
N=13
N=15
N=14
N=9
0%
Baseline
Wks
1-4
Wks
5-8
Wks
9-13
Wks
14-17
Wks
18-21
Wks
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22-26
B) Lantus Subjects using CGM*
N
27 (23 completed)
Age
11.0 ± 3.9 yr
Female
14 (52%)
Caucasian
25 (93%)
HbA1c
7.9 ± 1.0%
T1D duration
4.0 ± 3.1 yr
MDI Regimen
Glargine + RAIA*
Glargine + RAIA* + NPH
Other
21 (78%)
5 (16%)
1 ( 4%)
* DirecNet: Diabetes Care 31:525, 2008
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Lantus Subjects using CGM
Results – Glycemic Control
9.5
Baseline A1c > 7.5%
Baseline A1c ≤ 7.5%
9.0
HbA1c (%)
8.5
*
8.0
7.5
**
7.0
6.5
6.0
* p = 0.02
** p = 0.03
5.5
Baseline
Week 7
Week 13
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Lantus Subjects using CGM
Results – Glycemic Variability
Mean Amplitude of Glycemic
Excursion (MAGE, mg/dL)
180
Baseline A1c > 7.5%
Baseline A1c ≤ 7.5%
160
*
140
120
**
100
* p = 0.004
** p = 0.17
80
Baseline
Wks 1-4
Wks 5-8
Wks 9-13
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Lantus Subjects using CGM
Conclusions
• Use of the Navigator CGM was associated with an
improvement in glycemic control without an
accompanying rise in hypoglycemia
• Glycemic variability decreased with use of the
Navigator
• Subjects and parents reported high overall
satisfaction with the Navigator and did not
demonstrate deterioration in quality of life during 3month use
• CGM are tolerable and effective in children using MDI
regimens
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CGM Influences on Glucose Levels
Blinded vs Non-Blinded CGM Tracings:
p-value
• 21% less time <55 mg/dl
<0.001
• 23% less time >240 mg/dl
<0.001
• 26% more time in target
<0.001
(81 – 140 mg/dl)
(Garg et al, Diabetes Care 27:1922,2004)
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COMMON MISCONCEPTIONS OF CGM
(QUIZ)
1) “If I use CGM, I do not have to do BG checks anymore.”
Barbara Davis Center for Childhood Diabetes May 2008
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COMMON MISCONCEPTIONS OF CGM
2) “The starting of CGM will make diabetes management a
breeze – so simple!”
Barbara Davis Center for Childhood Diabetes May 2008
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COMMON MISCONCEPTIONS OF CGM
3) “The use of CGM will fix the diabetes – all blood sugars
will be perfect.”
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COMMON MISCONCEPTIONS OF CGM
4) “My CGM values should match my BG values.”
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COMMON MISCONCEPTIONS OF CGM
5) “The alarms will catch every low or pending low so I
don’t need to worry about lows anymore.”
Barbara Davis Center for Childhood Diabetes May 2008
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CLOSED LOOP (BIONIC) PANCREAS
“The Future”
i) Will probably come in parts
ii) JDRF supporting algorithm development
iii) Should reduce glucose highs, lows, and
fluctuations
iv) Will probably be more realistic than islet cell
transplant
v) FDA and medical insurance approvals (as with
CGM) will be critical
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Q. Why combine insulin pumps (CSII) and
Continuous Glucose Monitors (CGM)?
(p121)
A: “They complement each other tremendously
and provide the most ‘state of the art’ diabetes
care available.”
The CGM helps with:
•Cannulas dislodging
•Missed food boluses
•Hypoglycemia
•Corrections
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Our Initial Data:
1. Two oral presentations at ADA in June,
2008 (Abstract # 230-OR and 42-OR).
2. Our emphasis: Preventing severe
hypoglycemia at night.
3. This may be the first part of a closed loop
system acceptable to the FDA.
4. We have shown that 80% of pending
lows can be predicted.
5. Safety remains the primary goal.
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“Now let me get this right, Dr. Chase…
You want the elves to make an
artificial pancreas?”
THANK YOU
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