Sugar Surfing with a CGMStephen W. Ponder MD, FAAP, CDE

Managing “d” well requires…

• Comprehending a system with basic principles/concepts

• Adjusting to changing or shifting conditions/situations

• Frequent assessments and re-assessments

LIKE….• Driving a car• Flying an airplane• Walking a tightrope• Surfing

#01-01Sensor*/HemoCue Data

(29%)

50

100

150

200

27 TueMar 2001

28 Wed 29 Thu 30 Fri 31 Sat 1 Apr 2 Mon 3 Tue

Sensor Vs. HemoCue (Finger) Glucose --- Sensor # 6989 hCDP Output

Glu

cose

(mg/

dL)

Average Blood Glucose = 98 mg/dl

* Note: Investigational device. Device not approved by FDA

Appreciate the flux of sugar levels in non-d persons

Remember: Sugar Surfing is all about managing…

FLUXdrift

exercise insulin

“incoming” blood sugar

External Internal

metabolism

“outgoing”

Diabetes is best approached 1 day at a time

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

*

*

*

**

*

**

Don’t pass up an opportunity to assess a trending BG

• Choose what you consider “actionable”

• Set personal action thresholds• Use situational thinking: consider

recent, current and impending actions• Check your BG results over time• “treat to target” (repeat as needed, but don’t

“overstack” your insulin)

(Glucose production – Glucose disposal) = FLUX

Here is a picture of FLUX and DRIFT

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

Human circulatory system

165 pound (75 kg) man(5.1 grams)

55 pound (25 kg) girl(1.75 grams)

110 pound (50 kg) boy(3.45 grams)

= 4 gram glucose tabaka “glucose transit system”

static vs. dynamic diabetes carestatic• Actions predetermined• Minimal 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 constantly influence

subsequent actions• Training needed, plus ongoing

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

present

past future

REACTIVE PROACTIVE

Actions

Omissions

Actions

Omissions

A pancreas can’t predict the future

• It acts so fast it doesn’t need to.• Can shut off insulin immediately• Can release premade insulin• Insulin it releases can start

working in minutes• Can rapidly respond to shifts in

sugar levels

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

Traits of effective CGM usersWear it most of the timeCheck trend line oftenThey “work the lag” times

FOOD lagINSULIN lagSENSOR lag

Not afraid to experimentNot expecting perfection

Principles of Sugar Surfing1. A CGM is no better or

worse than the person responding to 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. Pre-empt when you can

“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

Turnaround Time : glycemic inertiaCorrections may need to be adjusted 10-20% to compensate

Goal: Try to stay between the lines

As your skills improve, lower the glucose for the upper alert

Timing 101 – 20 min. match

Insulin

Food

Timing 101 – 45 min. mismatch

Insulin

Food

Be realisticAccept that the first 6-12 months

are on a “learning curve”Set higher and wider targetsHave low expectations to startIt’s still a finicky technologyPLEASE BE PATIENT

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

Cal-i-bra-tion (noun \ˌka-lə-ˈbrā-shən\)• Comparing the sensor to an

accepted “standard” value• The accepted “standard” value is

a fingerstick BG level• So the sensor itself can be no

more accurate than the BG meter it’s compared to…or how well the BG meter was used

Calibration tips

• The first sensor day can be erratic as it “settles in”

• Don’t over calibrate!• Try to calibrate on a steady trend • Try to calibrate when in your

target range

CGM calibration tip…

steady

2 hours

Whenever possible: calibrate the CGM system when on a “steady” sugar trendline

2 hr “wait” time between “turning on” sensor and providing 2 calibration BG readings to start session

steady baseline

Daily calibrating on a steady baseline

Steady trend2 hours

Calibrate your CGM…On a steady trend when you can…

In the BG range you want to be most accurate in…

Steady trend

4 hours post start up calibration (extra)

Settling in at 6 hours: wobble

Sensors are not always right

Or is it the meter that’s off?

Morning madness?

After 14 hours after new CGM sensor insertion…

After calibrating with 112 mg/dl, the sensor immediately reads this

Take home message: a new CGM sensor site might take a day or so to properly “settle in” or “read” properly. Take this under consideration and don’t give up on a session too soon.

But BG meter calibration shows THIS…

Overnight basal testing

Overnight basal in range (glargine)

Overnight in range!

Overnight control in range

Basal testing…

Overnight basal control - Lantus

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

Why timing is everything

3 units @6:10 28 gm @ 6:50

Timing…waiting for the bend

“window”

3 U lispro @ 6:22AM

28 GM CHO @ 6:52AM

Timing insulin and meals to prevent a spike

Wait for the bend!!

6U @146 mg/dl Eat here @132

mg/dl

45 minutes

Wait for the “bend”!

Stopping sugar spikes

3 units (5:32AM)

Meal(5:48 AM)

?

Point “A” Point “B”

sugar trend

sugar trend

sugar t

rend

Insulin “correction”

Carb “correction”

~ 2 hours for insulin~ 15-30 minutes for carbs

Range of possible BG outcomes

“the trend is your friend”

Blood glucose level

Noticed rising trend at 1:43 PM: 165 mg/dl

Took 5 units lispro @ 1:45 PM

4 hours

Late BG rise after the morning: no lunch eaten 135 mg/dl @ 2 hours

“Direction affects correction ”

Although subtle, this can be “felt”

BG = 157 mg/dlInj 4 U lispro @3:15

2-3 hours

20-30 minA

B

C

Correction tips (on a steady trend)

A. Remember the lag time before insulin starts to effectively lower BG

B. Remember the length of time it takes to accomplish the desired task

C. Patience and practice make these kinds of results possible

Micro-bolusing (dosing)

Steady baseline BG trend

BG 136 mg/dl

2 units lisproWait 2 hours

Target zone

• Very advanced • CGM needed!• Note flat BG

“baseline” trend• Calibration good• Not “correction”

per se• More of an

“adjustment”

BG 137 mg/dl and rising slowly

3 units lispro

“Micro-bolusing”

BG 124 mg/dl injected 1.5 units lispro

@3:56AM

2 hours

Microbolus experimentation

Lag time

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

1.5 units

~ 2 hours

3U lispro@ 3:40AM

4 unit lispro “push”

“Course correcting for smooth sailing”

Well balanced basal insulin

6 unit “shove” at 133 mg/dl

2 hour correction

Mealtime insulin @ 8:30PM 7 units lispro

Duration of insulin 3hr

Slow BG rise fro

m fried meal

Insulin correction dose @ 2:53AM 6 units lispro

lag

2 hours to correct

Teaching points…

a. Know your insulin “umbrella”

b. Slow carbs cause unexpected highs

c. Insulin onset of action = lag time

d. Rise in BG levels has vector qualities

e. It takes time to correct a high

a

b

c

d

ea

b

6:53PM BG 108 inj 6 units

7:15-7:359:52PM BG 125↑ inj 4 units

“Effective duration” of insulin action: 3 hrs

“Active insulin” • Example: Slow carb

meal (fried food) • e.g., Chicken fried steak,

cream gravy and 3 onion rings and 8 French fries

• Estimated 60 grams: 6 units: inject 6 units lispro

• NO rise in BG for 3 hours, then rapid ascent

• Time until rise reflects “active insulin” effect

• Must do this many times and take the average

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

Rising BG trend (132 mg/dl) @ 2:06AM

5 units lispro @ 2:12

Fried Chicken

2.5 hours

8 U 6 U 5 U 5 U3 U Lispro

20 Lantus

“Inflections”

calibration

Tex-Mex Dinner

calibration

“Remember the Alamo”

Correction and meal

6 units (161 mg/dl)

Meal(26 gm CHO)

~ 45m126 mg/dl

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

5 units

Meal(25 gm CHO)

40 minutes

Correction with 20 grams carbs

20 gm CHO

121 mg/dl: 3 units @ 10:04PM

80 mg/dl: 7 units lispro @ 6:36PM

Meter: 55 mg/dl @ 7:56PM

My estimated duration of insulin action: 3.5 hours

Slow carbs

• Experimented here:• Ate a pasta meal at the

Olive Garden• Took a single insulin shot

(70 gm = 7 units)• Sugar dropped at time

of usual peak insulin action: ~60-90 minutes

• BG recovered without treatment

• Late rise in BG required second injection

Leveling off

Olive Garden2 salad

servings, 1 breadstick

and Lasagna

Slow BG rise

lispro

121 mg/dl: 3 units @ 10:04PM

80 mg/dl: 7 units lispro @ 6:36PM

Meter: 55 mg/dl @ 7:56PM

My estimated duration of insulin action: 3.5 hours

Fast insulin + slow carbs =

low BG• Ate a pasta meal at the

Olive Garden• Took a single insulin

shot (70 gm = 7 units)• Sugar dropped at time

of usual peak insulin action: ~60-90 minutes

• BG recovered without treatment

• Late rise in BG required second injection

• Notice the insulin-food “balance” and how it effects BG levels

Leveling off

Olive Garden2 salad

servings, 1 breadstick

and Lasagna

Slow BG rise

lispro

Insulin effect

Food effect

“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

3 units lispro

Breakfast

BG 173 mg/dl 5 units lispro

Meeting

A “random rise” in BG during a routine day.

2-3 hours

Working it…(i.e., glucose control exists “in the moment”)

~ 2 hoursOops! I Ate an EXTRA breakfast

taco!

BG 142 ↑ : took 5 units

hypothetical

real

And thirdly, the correction and carb ratios is more what you’d call ‘guidelines’ than

actual rules

“Most of our assumptions have outlived their usefulness”

Marshall McLuhan

8 U @ 9:30AM

7 U @ 10:54AM

6 U @ 12:29PM

60 grams carbs

Ultimately 21 U lispro

Insulin to carb ratios are only a start

7

5

4

5

Large bowl turkey soup and 2 small pieces cornbread @ 6:30

…flux?”

“What the…

Duration of insulin P

iz

za

9 units lispro for 90 gm Mexican food lunch @3:30

6 units lispro @ 6:30PM for rising BG after 3 hr IOB

Stabilization

Two gulps of juice (15-20g CHO)

5 gram CHO “nudge” @ 66 m/dl

Dropping < 1 mg/dl/min

“The nudge” (aka microcarbing)

5 gram CHO “nudge” @ 66 m/dl

Glucose counter-regulationGlucagonEpinephrineCortisolGrowth hormone

Leisurely walk from 7:00 to 8:30: straight line

Exercise “bump up”Moderate intensity75 minute durationGlycogen Glucose

2 units

1 hr walk

“Walking down” a trend

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

127 mg/dl @4:47AMInjected 3 units lispro

1.5 hours

“Pushing sugar”

BG 137 mg/dl : dose 5 U lispro

Lag time

Eat breakfast here

Timing insulin and food is like shooting clay pigeons

6 U lispro @ 1:45AM @ 170 mg/dl

30 min lag

3 hour wait

Taking the drop…

“Taking the drop”

BG 160 mg/dl @ 1:47AMInjected 5 units lispro

Lag time

Drop time 2-3 hrs

perfect bottom turn

froth

Woke up at 3:55AM at 184 mg/dl

Took 4 units lispro

Wait (slept) about 3 hours

Bingo!

Tamale Soup at dinner (slow carbs, slow rise)

“Livin’ la vida Gluco”

182 mg/dl : 7 units lispro

Insulin lag time 30-40 min

Eat breakfast here

Food lag time

124 mg/dl

Timing is everything…do you have the patience or the time?

Slow BG rise overnight from

fried meal

BG drop time20-30 min

Missed 9PM basal dose (glargine)

Normal timeLantus taken (9PM)

Detected rising sugar level @ 2AM

Humalog dose (7U) AND usual Lantus taken (20U)

Sensor “gap”!!

dinner

Fell asleep!

All back in range by morning!

What happens when a basal insulin dose is missed

Usual time Lantus dose is taken: 9PM

Rising BG discovered here

Insulin correction given

If not treated: high BG and ketones

Treated: In range BG and NO ketones

Stress effect

Endocrinology Board Exam taken every 10 years

Stress and Sugar• Strong emotional stress

triggers release of a several hormones

• These hormones act on liver and muscle to cause the release of internal sugar from depots inside the body

• Stress hormones also make the liver produce sugar from substances like protein and fat

• This can overwhelm the ability of basal insulin to dispose of sugar faster than it can build up in the blood

• CGM allows for more aggressive anti-stress treatment of rising sugars

Crossing 140 mg/dl @ 3AM and a 2.5 U lispro correction

~ 2 hours

Lag time

Why act?• Slow upward BG trend

(red arrow)

• Crossed personal “action consideration” threshold: 140 mg/dl in my case (yellow line)

• Knew the CGM would alert me to a rapidly dropping BG later if I over treated

• Have done this many times before: practice, practice, practice

Slow gradual overnight rise in blood sugar

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

Awakened by CGM alarm to a BG below 60 mg/dl

Slow gradual overnight fall in blood sugar

Lag time

20gm

Rationale• Slow downward BG trend

(red arrow)

• Crossed personal “action consideration” threshold: 60 mg/dl in my case (yellow bottom line)

• Drank 20 gm grape juice and went back to sleep

• Knew the CGM would alert me to a rapidly rising BG later if I over treated

• Have done this many times before: practice, practice, practice

This can be “felt”

This can be “sensed too”

CHO

A steady trend

The body’s defenses against low blood sugar

include the brainDownward shifts, even small, can be sensed by

the conscious brain Once sugar levels off, the brain senses

stability

Rationale• Blood sugar control is

complex, it includes the brain and nervous system

• Long term damage to the autonomic nervous system can result in loss of classic signs/symptoms of low blood sugar

• But, the brain itself might still retain the ability to sense downward sugar shifts before severe low BG kicks in (e.g., < 50 mg/dl)

• A CGM device can serve as a “biofeedback” device of sorts in adults willing to develop the ability over time.

Feel the drop and level off

Subtle correction• BG 125 and rising• Took 4 units lispro• 2 for the slow rise• 2 for the

correction• Waited almost 2

hours (yellow arrow)

• Notice lag time before BG “turns” (red arrow)

This rise can be sensed

This feels stable This also “feels” stable

> 1-2 mg/dl/min

~ 1 mg/dl/min

“Working down” a rising BG

4 units @ 173 mg/dl

2 units @ 167 mg/dl

7 units @ 2PM for Whataburger and rings

Rise

4 units Humalog @ 11:07PM

BG rising after insulin effect is“waning”. BG = 146 mg/dl

Dinner (soft tacos, refried bean and

chips/salsa); 7 units lispro taken 20 minutes

premeal at 7PM

My “DIA” = 3-4 hours

Slow drop over 6 hours

Notice the obligatory “lag time”!

Anatomy of a preemptive correction

Anatomy of a nighttime low

A) 4 hour window

B) 24 hour window

C) 6 hour window

D) Resolution

34 mg/dl

36 grams CHO

2.5 hours

6 month CGM data summary

Average BG = 103 mg/dlStandard deviation = 34 mg/dl

Aim to keep the average BG in range and the standard deviation AT LEAST HALF the average BG value

Day vs. Night: any thoughts about why?

Interpret these two images

Hint: sensor is over two weeks old

What is it a good time for and why?

Straight line trend

Straight line trend

= 10 grams carbs

60 mg/dl

90 mg/dl + 30 mg/dl

6 U

4 U

4 U 4 U

5 U

6 U

28 GM

90+ GM

1. Stacked insulin + delayed eating2. “Hyper-treated” severe low3. Fought “rebound” high BG all night4. Took the drop and timed meal

Dislodged insulin pump site…Picked up early by CGM

Pump site changed, insulin dose given, carb correction taken…$13,000 saved

Penny stock day trading strategyCGM is “sugar surfing”

board

©

“Kickin’ D’s Butt”