Insulin Pumps and Sensors
Eric L. Johnson, M.D.
Assistant Medical Director
Altru Diabetes Center
Assistant Professor
Department of Family and Community Medicine
University of North Dakota
School of Medicine and Health Sciences
Objectives
• Discuss basic operations of
pumps and sensors
• Discuss suitable patient types for pump
and/or sensor use
• Discuss insulin kinetics in the context of
pump and sensor use
• Discuss advanced operations of pump
and sensor devices
3 Factors for Glycemic Control
with a Pump
• A1C
– current standard for diabetes control
(ADA, AACE)
• Standard Deviation
– Measure of Glycemic Variability (Range)
• % of time <70 mg/dl
- too many lows>>lower A1C
Medtronic
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Continuous Subcutaneous Insulin Infusion
(CSII)
‘Insulin Pumps’
Technology origins 1960’s, really
advanced in the last decade
Deliver insulin continuously (‘basal’)
and for food (‘bolus’)
Current technology still requires significant
user interface
DON’T hook up, turn on and
forget about them
Continuous Glucose Monitoring
(Sensors)
• Technology developed over the last
decade, clinic use first, now also
home use
• Record glucose 24/7, usually displayed
every 5 minutes
• Record interstitial fluid glucose, not serum
or capillary, generally ~15 min ‘lag’
Pumps and Sensors
• Interfaced devices developed
last 3 to 4 years
• Still not “closed loop”
• Patient gets info, has to act on it
• Many have high/low alarms,
trends alarm (rapid rise or decline)
What Do Pumps Not Do?
• Take over care of patient’s diabetes
• Make diabetes perfect
• Lessen the “workload” of diabetes
(it’s just different)
• Still need to do the basics…….
What Do Pumps Do?
• Mechanically deliver insulin to the
subcutaneous tissue through plastic tubing
and/or small plastic or metal catheter
• Small ‘computers’ in the pump assist the
user in delivering proper basal and bolus
insulin dosing
What Do Pumps Do?
• Only rapid acting insulin is used
• Some is delivered continuously units/hour
(like an insulin drip) (‘basal’)
• Some is delivered ‘bolus’ with food
• Insulin is absorbed more consistently
What Do Pumps Do?
• Different basal rates at different times of
day (good to match activity)
• Bolus insulin all at once or
deliver over a specified time period
• Potentially less variability and lower A1C
• More recent data strongly supports
pump/sensor use (STAR 3 trial, others)
JDRF NEJM Oct 2008
STAR 3 trial N Engl J Med. 2010 Jul 22
French Study Journal of Pediatrics 2010
Normal Insulin Production:
The Pancreas
A healthy pancreas releases insulin automatically, on
average, every ten to 14 minutes1, in amounts appropriate
for varying blood glucose levels.
 Normal Insulin Secretion
Insulin
Bolus dose
Basal dose
0 hr
12 hrs
Adapted from 1. Marchetti, P, et al. Diabetes, Vol 43, p. 827-839, June 1994.
Schematic representation only
24 hrs
Basal / Bolus Therapy
Insulin Pump
Insulin Needs
Bolus Insulin
Basal Insulin
-Variable basals (not fixed)
-Bolus-Immediate, Square, Dual Wave
Time of Day
Continuous Glucose
Monitoring Systems
(CGMS) (Sensors)
What Do CGMS (Sensors)
Not Do?
• Completely eliminate the need for
fingerstick blood glucose testing
(although it’s a lot less)
• ‘Take over’ diabetes control
• Give 100% data all of the time
What Do CGMS (Sensors) Do?
• Potential for less variable blood glucose
JDRF study, NEJM 2008 STAR 3 NEJM 2010
• Potential for less apprehension at work, at
school, while sleeping, or driving
• Give good data a majority of the time
• Glucose value every 5 minutes
• High/low alarms
Patient Selection for
Sensors/Pumps
Patient Selection
• Mature, accepting of diabetes
• Psychologically stable
• Good with technologyCan text a photo on a cell phone?
• Younger patients don’t think of these as
exotic electronic devices
• Don’t let technology bias influence
negatively
Patient Selection
• Compulsive enough to do fingerstick
glucose 4 times or more daily
• Will not need as many fingersticks
with sensor, but it requires frequent
attention
• Generally will not ‘motivate’
nonadherent patient
Patient Selection
• Patients who are not meeting goals on
multiple daily injections
• Usually patients who are good
with followup
(phone/in person/e-mail/appointments)
• Patients with a lot of variability
• Patients with asymptomatic hypoglycemia
• Usually start pump first, add sensor later
(2 to 4 weeks)
Patient Selection
• Selecting proper patients is important
to maximize success
• Proper training and followup are critical
for success
Pumps and Sensors
Animas
Omnipod pump with remote
Not shown- “patch pumps”
Investigational
Navigator CGMS
Medtronic Minimed
White Board Concepts
• Use your brain as a pancreas
• Different Basals, Different Boluses
• What does insulin really do? Myths
What?!?! It’s not instant?!?
• Successful bolusing:
hit the receiver down the field!
• What are square and dual wave boluses?
• What is standard deviation?
CGMS Data
Pregnant patient on pump + sensor
Note +/- BG
Note % basal vs. % bolus
Fingersticks and Boluses
Average is high ~200, lots of variability
Note large number of correction boluses
+/BG
AUC
Tips for More Successful
Pump Use
• Change insulin infusion sites every 2 ½ to
3 days. No exceptions
• Pump infusion sites can degrade with high
level, vigorous exercise
• Protect from heat/sun/cold
Tips for More Successful
Pump Use
• Advanced features. Use Them! Alarms,
dual wave bolus, variable basals
• Elevated Blood Sugar, no response from
correction bolus- take a shot, change out
Tips for More Successful
Sensor Use
• Calibrations are MUCH better if done during a
time of blood sugar stability
• If calibrations are done when blood sugars
are changing relatively rapidly, you may
actually be amplifying error
• Wash hands/avoid hand sanitizer for best
fingerstick results
Tips for More Successful
Sensor Use
•
•
•
•
Ideal fingersticks have a +/- of up to 15%
Ideal sensors have a +/- of about 15%
It's unlikely that they will match exactly
Fingerstick blood sugars at values
>280 or <80 aren't as good for calibrating
Tips for More Successful
Sensor Use
• Sensors are typically 15 or 20 minutes
behind
• Transmitter may need charging if
values/data are poor quality
Tips for More Successful
Sensor Use
• Initially, low alarms should be no lower
than 80, and high alarms should be
220-240
• Patients have a lot more glucose variability
than they think
(“my control is terrible on this thing”)
Tips for More Successful
Sensor Use
• If patients tell you their alarms are going
off all the time,
• It's usually not the pump and sensor
that are the problemtheir insulin/activity/food are what need
to be changed
Summary
• Insulin pumps are excellent tools for
diabetes management
• Sensors are excellent tools for diabetes
management
• Still need to do basic diabetes cares
• Choose patients selectively for best results
• Training and followup are critical
for success
Contact Info/Slide Decks/Media
e-mail
eric.l.johnson@med.und.edu
ejohnson@altru.org
Phone
701-739-0877 cell
Slide Decks (Diabetes, Tobacco, other)
http://www.med.und.edu/familymedicine/slidedecks.html
iTunes Podcasts (Diabetes)
http://www.med.und.edu/podcasts/ or iTunes>>search UND Medcast (1/21/10 release)
WebMD Page:
http://www.webmd.com/eric-l-johnson
Diabetes e-columns (archived):
http://www.ndhealth.gov/diabetescoalition/DrJohnson/DrJohnson.htm