Page 251 - Glucose Monitoring Devices

258 CHAPTER 13 Low glucose suspend systems

treated participants [8]. However, during the long-term observational phase of EDIC,
where the HbA1c levels were similar between groups, severe hypoglycemia was not
different between groups [12]. Moreover, recent data show a comparable prevalence
of severe hypoglycemia across different HbA1c ranges in both adolescents and adults,
including the elderly [13,14]. Hypoglycemia is also common among patients with
T2D treated with insulin. In a 2013 study, 97,648 emergency visits per year were
ascribed to insulin-induced hypoglycemia, and the incidence of hypoglycemic events
was twice as high in individuals older than 80 years old, resulting in a projected cost of
$640 million in healthcare expenses [15]. Other complications of hypoglycemia
include an increased risk of cardiovascular events and cognitive deficits in older adults
with diabetes [16,17]. Thus hypoglycemia is a major obstacle in achieving optimal
glycemic control in insulin-treated patients with diabetes.
Hypoglycemic events have decreased with the introduction of insulin analogs such
as insulin glargine U100 and insulin detemir compared to previous generations of
intermediate-acting insulins such as neutral protamine Hagedorn and longer-acting
ultralente insulins (now discontinued worldwide) [18]. Moreover, newer longer-
acting insulin analogs such as insulin glargine U300 and insulin degludec have
been shown to reduce the rate of symptomatic hypoglycemia by 20%e30% compared
to insulin glargine U100 in patients with T1D and insulin-treated T2D [19e21].
However, severe hypoglycemia, particularly nocturnal, continues to pose a risk with
insulin therapy. Insulin pump therapy and the use of continuous glucose monitors
(CGM) have been shown to improve glycemic control and reduce the risk of hypogly-
cemia [22,23]. However, sensor-augmented pump therapy does not eliminate
nocturnal hypoglycemia completely [24]. Moreover, most youths with T1D do not
meet the glycemic A1c goal of below 7.5% (for children) or 7% (for adults) as defined
by the American Diabetes Association and International Society for Pediatric and
Adolescent Diabetes [25]. The open-loop insulin delivery system (use of insulin
pump and/or CGM without automation) is subject to human error and can cause
unexpected hypo- and/or hyperglycemic events. Therefore closing the loop by
integrating insulin pumps and CGMs using necessary algorithms offers promise in
the reduction of overall and nocturnal hypoglycemia, meal-related hyperglycemia,
and wide glucose excursions as measured by different indices of glycemic variability.
Other chapters in this book have provided detailed information on various
closed-loop systems. This chapter focuses only on the low glucose suspend feature
of the closed-loop system.

Low glucose suspend system
For patients with T1D, more than half of hypoglycemic events occur at night. In
younger individuals with T1D, more than 75% of hypoglycemic seizures and 6%
of deaths can be attributed to nocturnal hypoglycemia in children [26]. In both
children with T1D and their parents, fear of hypoglycemia is associated with poor
quality of life [27]. Additionally, hypoglycemia begets hypoglycemia [28].