Optimizing Continuous Glucose Monitoring (CGM)

Utilizing your CGMS to the MaxStephen W. Ponder MD, FAAP, CDE

What can a CGMS help you do?Continuous Glucose Monitoring System

• Prevent after meal BG spikes• Correct low & high BG more accurately• Prevent/minimize severe low blood sugars• Teach you how to sense subtle shifts in BG• Reduce the fear of lows, especially at night• Lower the A1C levels• Help to make diabetes work for YOU• Feel more “normal” (perhaps even confident)

What I will not be discussing…• Costs of different CGM devices

– That depends on your insurance– There is a cash price too

• How to purchase a CGM device– Operators probably standing by now– Need Rx to get insurance to consider

paying

• How to insert or start up a CGM– There are trainers and apps for that

Principles of advanced CGM use1. A CGM is no better or

worse than the person wearing it.

2. If you can measure it, you can predict it.

3. Flux and drift happen… manipulate them!

4. Keep your eye on your line.5. The trend is your friend6. Learn lag limits; be patient

7. Zero in on your zone8. Master micro-dosing9. Factor in glycemic inertia

and insulin momentum10. Don’t let “good enough”

be the enemy11. Calibrate carefully12. CGM as “sugar surfing”

or “day trading”

“Chance favors the prepared mind” Louis Pasteur

• Estimates sugar level from interstitial fluid

• Calibrated with fingerstick blood sugar levels at least twice daily

• Readings provided every 1 to 5 minutes

• Drift and imprecision are possible

24 hour glucose plot – A1c 5.7%

1st Rule of CGM:Your blood sugar levels are unique.Trends and patterns are what’s important

Diabetes control exists largely in the momentNo two days are ever the same…

Each day is unique…

“You can never step into the same river; for new waters are always flowing on to you.” Heraclitus of Ephesus

8 versus 1440 “decision points”

7:03 115

9:33 129

12:15 95

3:34 131

6:12 168

9:49 107

11:53 114

3:05 132

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*

*

*

*

*

*

*

CGM is like shining a flashlight in a dark room of moving objects

Meters are commodity items“a commodity is the generic term for any marketable item

produced to satisfy wants or needs”

• The best BG meter is the one you’ll use

• $10.41 for 50 strips (Medicare 2013 rate)

• Lancing devices (avoid the nerves)

• Ketone meter (get one!)

ISO and FDA allowable errors

• 20% for 95% of BG values 75 mg/dl

• 15 mg/dl for 95% of BG values 75 mg/dl

• 5% “outliers” of ANY DEGREE of magnitude

“Glycemic Roulette”?

Diabetes Spectrum Volume 25, Number 3, 2012ISO 15197 Standards for SMBG

95 mg/dl

114 mg/dl

76 mg/dl

223 mg/dl

52 mg/dl

95% of the time

Oops!

Oops!

5%

5%

Calibration advice

• A CGM’s accuracy is no better than its calibration. • So…minimize variance whenever possible• Calibrate (if possible) when things are steady• Wash hands; get proper sized blood sample

(repeat if needed)• If you calibrate when high or low, do some more

later when back “in your zone”• You can over-calibrate too.

Remember: D-care is about managing sugar…

FLUXdrift

(Glucose production – Glucose disposal) = FLUX

Here is a picture of FLUX

Non-diabetic persons

Sugarlevel

In Out

Why do blood sugar levels shift all the time?

How much sugar is in the bloodstream for a 100 mg/dl BG level?

Human circulatory system

75 kg man(5.1 grams)

25 kg girl(1.75 grams)

50 kg boy(3.45 grams)

= 4 gram glucose tab

present

past future

REACTIVE PROACTIVE

Actions

Omissions

Actions

Omissions

static vs. dynamic diabetes carestatic• Actions predetermined• Minimal to no flexibility:

RIGID• Outcomes don’t

immediately affect subsequent actions

• Easy to teach/learn• Less time-intensive• Favors concrete thinking• Less motivation needed

dynamic• Actions are dependent on

situation/circumstance• Flexible and adaptable• Outcomes influence

subsequent actions• Training needed, plus

ongoing reinforcement• More time intensive• Favors problem-solving• Requires motivation

Ways to use RT-CGM technology

“Burglar alarm” “Surveillance system ”

Set “actionable” thresholds• Upper/Lower limits

– 80 mg/dl and 140 mg/dl– 90 mg/dl and 180 mg/dl

• Rates of change– Up or down arrows

• Factor in recent/current/future events as you are able

• Test your skills, experiment a little within reason

A pancreas can’t predict the future

• It just can act very fast so it doesn’t have to.

• Can shut off insulin immediately

• Can release preformed insulin

• Insulin released can start working in minutes

• Can respond to rates of change in sugar levels

Soldier: Come on. Let me show you.Soldier: The secret to this game is no matter what happens,Soldier: never, ever take your eye off the ball.Gump: All right.Gump: For some reason, ping-pong came very natural to me.

Traits of effective CGM users• Wear it all the time• Check trend line often• Work the “lag” times

– FOOD– INSULIN– SENSOR

• Not afraid to experiment• Not expecting perfection

Penny stock day trading strategyCGM - glycemic “day trading” tool

“sugar surfing”

BG awareness vs. alarm fatigue• Set reasonable alarm

thresholds– Depends on your goals

• Avoid high spikes?• Avoid lows?• Toddler? Child? Teen? Adult?

• Make sure you can hear/sense the alarm

• Anticipatory action can minimize alarms

Living with a CGM

• Keeping up with receiver (if not part of pump)• Keeping up with meter/strips/lancing device• Sensor unit size and longevity (recycling)• Showering/bathing/changing clothes• Taping and securing• Air travel (security and seating)• Acetaminophen can cause “headaches” (Dex)• Charging up/downloading• Logging events

Taping tips

Two week site before taping

Site after 32 days

Bruise from CGM sensor

Sensor depths

Medtronic Abbott

Sensor after 32 days

Dexcom G4

Day in the life…

Another in range day

A nice day…

A nice day…BUT…

7 units

5 units 3 units

Pasta

J

“Fried-food revenge” and correction

Fried food earlier in evening @ 8PM

BG = 1946 unit correction @ 7AM

BG = 115 in 3 hours

“Revenge of the Ribeye” and “The Insulin Strikes Back”

SLOW RISE

BG 167: 4 units

CORRECTION

LAG

2-3h

Slow BG rise from protein-fat laden meal

Slow overnight rise and early AM correction

Correction at 2:45 AM after slow post dinner rise with 5 units

5 units

~ 2 hours

Overnight rise, correction and meal

Steady in-range BG trend

Overnight basal testing

Overnight basal in range (glargine)

Overnight in range!

Overnight control in range

Basal testing…

Overnight basal control - Lantus

Time to correct

> 2 hours

Corrections take time

Time to reach 100 mg/dl (at ~ 4 mg/dl/min)

minutes

Blo

od s

ugar

180

260

340

420

4 mg/dl/min

Fine tuning a correction…

62 mg/dl

8gm

Timing 101 – 20 min. match

Insulin

Food

Timing 101 – 45 min. mismatch

Insulin

Food

“THE TREND IS YOUR FRIEND”CHECKING INSULIN BOLUSES WITH CGM

6 pm 8 pm 10 pm

300

200

100

60

Carb bolus Correction bolus

6 pm 8 pm 10 pm

Goal: green lines

Learning from the Line Graph – Effect of Exercise

2p 4p

70140

210

350

280 Bike ride – 60 minutes

E

2p 4p

70140

210

350

280

E

No insulin adjustment w/ basal rate reduction

CHO

Learning from the Line Graph – Correction dose

70140

210

350

280

8a 10a

“Stacked” insulin

I I 70

140

210

350

280

Blood glucose: 212 mg/dl

Correction dose: 5.5 units

I

Proper correction

Blood glucose: 212 mg/dl

Correction dose: 5.5 units

Correction dose: 3.5 units

12p 8a 10a 12pCHO CHO

Learning from the Line Graph – Insulin Timing

8a 10a

70140

210

350

280

8a 10a

70140

210

350

280

TodayYesterday

Insulin bolus: 7:30 AM

Breakfast: 7:30 AM

Insulin bolus: 7:10 AM

Breakfast: 7:30 AM

MI MI

Learning from the Line Graph – Effect of Food

8a 10a

70140

210

350

280

8a 10a

70140

210

350

280

TodayYesterday

Bagel Breakfast Oatmeal breakfast

M I M I

Don’t Stack your Insulin!

Slide courtesy of Jen Block RN, CDE and Stephen Ponder MD CDE

Learning from the Line Graph – What would you do?

4:30 pm 6:30 pm

70

140

210

350

280

1. What did I do?

2. What am I doing?

3. What will I be doing?

4. What do I need to do?

Learning from the Line Graph – What would you do?

12:30 pm 2:30 am

70

140

210

350

280

1. What did I do?

2. What am I doing?

3. What will I be doing?

4. What do I need to do?

Learning from the Line Graph – What would you do?

12:30 pm 2:30 pm

70

140

210

350

280

1. What did I do?

2. What am I doing?

3. What will I be doing?

4. What do I need to do?

What would you do next?

How would you categorize this?

4 day non-diabetic CGM plot

Turnaround Time : glycemic inertia

Corrections may need to be adjusted 10-20% to compensate

Goal: Try to stay between the lines

As readings improve, lower the glucose for the upper alert

112 mg/dl to 78 mg/dl after 1.5 units by injection on a “steady” BG baseline

1.5 units

~ 2 hours

Correction

~ 80m

~ 25m

5 units @ 5:43AM; 25 gm CHO @ 6:23AM

5 units

Meal(25 gm CHO)

40 minutes

Calibrate during a steady baseline

Calibrating with extreme BG levels can distort accuracy. Try to calibrate within your desired target zone range.

“Microcarbing” with CGM monitoring

2 gm CHO

Before 2 grams CHO After 2 grams CHO

Blood sugar correction 160 mg/dl to 100 mg/dl in 2 hours with 4 units insulin lispro by injection

4 units

~ 2 hours

Correction: 151 mg/dl to 103 mg/dl with 2 units insulin lispro after walk

2 units

~ 2 hours

Optimal lunch coverage

5 units

Stopping sugar spikes

3 units (5:32AM)

Meal(5:48 AM)

Calibrate during a steady trend

Calibrate on a steady line whenever possible

103 mg/dl

97 mg/dl

Steady

Calibrate during a steady trend

Correction and meal

6 units (161 mg/dl)

Meal(26 gm CHO)

~ 45m126 mg/dl

Correction with 20 grams carbs

20 gm CHO

Skipped data (out of range?)

Sensor starting to lose integrity at 32 days

14 days of use32 days of use

Sensor confusion?

Sensor confusion?

Duration of insulin effect can be determined here

~ 4 hours

IOB after 6 units and fried meal

6 units

3.5-4 hours 2 units

WalkFried Meal

Walking down a trend

2 units

1 hr walk

Wait for the bend!!

6U @146 mg/dl Eat here

@132 mg/dl

45 minutes

Wait for the “bend”!

Stress effect

Microbolus at 7:55AM when BG was 151 mg/dl took 2 units (after surgery)

Although subtle, this can be “felt”

First…figure out your favorite foods

Why do lows happen at night?

• Hormonal patterns• Lower insulin need• Insulin peaks?• Post-exercise effect• Snacking stacking?

Lower overnight insulin/add snack

Don’t pass up an opportunity to correct a high (or low) BG

• Choose what you consider “actionable”?

• BG above or below chosen thresholds

• Consider recent and impending actions

• Check your results with BG levels

• Repeat as necessary

Curb your liver!

• The liver makes as well as stores sugar

• A proper insulin level “calms down” the liver

• Aim for an in-range sugar level (<120 mg/dl)

upon waking up each day

Check your targets often• Make sure you hit

your target “zone” sugar (± 30 mg/dl)

• Rapid-acting insulin results are best examined at 2-3 hours

• Results should feedback to the next attempt

“Practice makes better”

D-teens count carbs POORLY

23%

clinical dietitian (n.)

1. A person specializing in medical nutrition therapy.

2. An underappreciated and underpaid member of the diabetes team.

3. Someone who can help your left brain

We have > 60,000 thoughts daily

• Groups of thoughts comprise decisions

• The typical non-D person makes ~ 250 decisions a day about food

• How many more food choices does a PWD/CWD make?

“What are we doing for dinner, dear?”

Eat at home

“You can delegate authority but you can’t delegate

responsibility”

Do 2 RN’s = 1 kid?

=

Ok? Ok to me!

Concrete thinkers* can’t…

1. Consider a hypothesis2. Consider multiple

possibilities in a scenario

3. Systematically solve a problem

4. Use combinatorial logic

*Lasts until 15-17 years of age*25% of adults are concrete thinkers.

Diabetes CONTROL results as much (if not more) from what you

choose NOT TO DO as it results from what you choose TO DO

Principles of advanced CGM use1. A CGM is no better or

worse than the person wearing it.

2. If you can measure it, you can predict it.

3. Flux and drift happen… manipulate them!

4. Keep your eye on your line.5. The trend is your friend6. Learn lag limits; be patient

7. Zero in on your zone8. Master micro-dosing9. Factor in glycemic inertia

and insulin momentum10. Don’t let “good enough”

be the enemy11. Calibrate carefully12. CGM as “sugar surfing”

or “day trading”

Questions?