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Hybrid Closed-Loop Systems Prove Safe And Effective in Controlling
Glucose Levels in Children and Adults with Type 1 Diabetes
Results of two trials demonstrated safety and efficacy, and reduction in exercise-induced hypokalemia, using closed-
loop systems in children and adults with type 1 diabetes. Results of the two trials were reported at the American
Diabetes Association’s 77th Scientific Sessions, from June 9–13.
C
ontinuous glucose monitoring
devices provide around-the-clock
information on blood glucose lev-
els in patients with type 1 diabetes. Insulin
pumps allow insulin to be administered
subcutaneously throughout the day.
Over the recent past, researchers com-
bined the technology of continuous
glucose monitoring and insulin pumps to
form closed-loop systems, which allow for
continuous insulin delivery through a pump
throughout the day and night based on
glucose measurements provided every 5
minutes by the continuous glucose monitor.
Hybrid closed-loop indicates that the
system is continuously adjusting insulin
delivery. At mealtime, however, the patient
enters the amount of carbohydrates being
consumed, and the insulin pump deter-
mines the meal dose of insulin.
Hybrid Closed-Loop System in
Children Age 6–12 Years With Type 1
Diabetes Using a Personalized Model
Predictive Control Algorithm
Bruce A. Buckingham, MD, of the Lucile
Salter Packard Children’s Hospital, Stanford
University in Stanford, California, explained
that children with type 1 diabetes are more
sensitive to insulin than adolescents and
adults, and are at increased risk of severe
hypoglycemia overnight.
Dr Buckingham and colleagues performed
an inpatient research center study to eval-
uate the safety and feasibility of a new
hybrid closed-loop system. They combined
a patch pump with Bluetooth-enabled
sensor built into the receiver and a person-
alized model predictive control algorithm.
The study included 12 children aged 6-12
years with type 1 diabetes whose average
age was 9 years and average diabetes
duration was 4 years. The trial consisted
of a 36-h, inpatient, closed-loop assess-
ment with meals ranging from 30-90 g of
carbohydrates and limited physical activity
to examine glycemic outcomes.
Continuous monitoring data indicated
that 69.2% of overall glucose values were
between the desired range of 70-180 mg/
dL. Overnight, 82% of values were within
range. Participants’ average glucose level
was 157 mg/dL, and 2% of readings were
<70 mg/dL using the system compared to
4% of readings <70 mg/dL when at home
and not using the hybrid-closed loop sys-
tem. Mean fasting glucose level following
overnight use of the closed-loop system
was 136 ± 24 mg/dL.
Dr Buckingham concluded that the auto-
mated glucose control algorithm performed
well and was safe during day and night use
in children with type 1 diabetes.
“Hybrid closed-loop systems do a great job
improving glucose control overnight, low-
ering the risk of hypoglycemia significantly,
and allowing patients and their families to
get a good night’s sleep,” he said.
“These systems also assist patients dur-
ing the day in decreasing the magnitude
of both high- and low-glucose fluctuations,”
he added. “Many patients prefer wearing
an ‘untethered’ patch pump, which pro-
vides more flexibility to enjoy physical
activities without worrying about infusion
set detachments.”
He continued, “The hybrid system provides
additional protection against hypoglyce-
mia, resulting in improved quality of life
for children with diabetes. Longer outpa-
tient studies are needed in subjects using
the system under their home living condi-
tions. The device is being tested in many
age groups and under many different
conditions.”
Single and Dual-Hormone Closed-Loop
Glucose Control with Automated
Exercise Detection to Prevent
Hypoglycemia in Type 1 Diabetes
Peter G. Jacobs, PhD, of Oregon Health &
Science University in Portland, explained
that patients with type 1 diabetes encounter
difficulty in controlling their blood glucose
levels while exercising.
Aerobic exercise can cause sharp drops
in blood sugar, leading to hypoglycemia.
Single- and dual-hormone closed-loop
systems automate the dosing of insulin, or
insulin plus glucagon, to help these patients
avoid exercise-induced hypoglycemia by
reducing insulin delivery and increasing
glucagon in response to exercise.
Dr Jacobs and colleagues developed
and evaluated single- and dual-hor-
mone closed-loop systems. They set out
to determine whether exercise-related
hypoglycemia can be reduced through a
closed-loop system that responds to phys-
ical activity automatically.
The study included 20 adults with type 1
diabetes who used wearable, wireless sen-
sors including heart rate and accelerometer
sensors to detect the onset of aerobic
exercise automatically and communicate,
calculate, and deliver the appropriate insu-
lin and/or glucagon dose needed to avoid
hypoglycemia.
In random order, participants used various
systems, including:
•
A single-hormone closed-loop system
that doses insulin only
•
A dual-hormone closed-loop system that
doses both insulin and glucagon
•
A predictive, low-glucose suspend
system that shuts off insulin if glucose is
predicted to go too low
•
Patients’ usual current standard of care
whereby they controlled their glucose
levels using their own methods
Participants attended four, 4-day outpa-
tient visits at which they exercised for 45
minutes at 60% VO2max on days 1 and 4
in a human performance lab. They com-
pleted at least one at-home exercise
session to determine the amount of time
in hypoglycemia.
Subjects entered estimated carbohy-
drate intake into the insulin pump, which
automatically delivered a portion of the
© ADA/Todd Buchanan 2017
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