Response to nocturnal alarms using a real-time glucose sensor.
BACKGROUND
The objective of this study was to determine how subjects responded to alarms for hypo- and hyperglycemia while they were sleeping.


METHODS
Twenty subjects with type 1 diabetes (4-17 years old) were admitted to a clinical research center for approximately 24 h. Each subject wore two GlucoWatch G2 Biographers (GW2B) (Cygnus, Inc., Redwood City, CA) and was videotaped using an infrared camera from 9 p.m. to 7 a.m. The videotapes were reviewed to determine if the GW2B alarms were audible on the tape and to document the subject's response to the alarms. Because many alarms can occur surrounding a change in blood glucose, GW2B alarm "events" are defined as a one or more alarms separated from previous alarms by more than 30 min.


RESULTS
Downloaded data from the biographers identified 240 individual alarms, 75% of which occurred while the subject was sleeping. Of the 240 alarms 68% were audible on the videotape. Subjects awoke to 29% of individual alarms and to 66% of alarm events. Subjects 4-6 years old responded to 17% of alarms, 7-11 year olds responded to 20% of alarms, adolescents responded to 53% of alarms, and parents responded to 37% of alarms. Subjects awoke to 40% of the first alarm during the night, but to only 28% of subsequent alarms. There were 11 events when the glucose was confirmed to be < or = 70 mg/dL, and in each case the subject was awoken. Fifty-five percent of alarm events occurred when there was no hypo- or hyperglycemia confirmed by a reference glucose value.


CONCLUSIONS
Subjects awoke to 29% of individual alarms and to 66% of alarm events. Subjects awoke during all alarm events when hypoglycemia was confirmed, but there was a high incidence of false alarms.
Buckingham
Bruce
B
Stanford University School of Medicine, Stanford, California 94305-5208, USA. buckingham@stanford.edu
Block
Jen
J
Burdick
Jonathan
J
Kalajian
Andrea
A
Kollman
Craig
C
Choy
Michael
M
Wilson
Darrell M
DM
Chase
Peter
P
D000293:Adolescent; D001786:Blood Glucose / Q000378:metabolism*; D002138:Calibration; D002648:Child; D002675:Child, Preschool; D003922:Diabetes Mellitus, Type 1 / Q000097:blood*; D004868:Equipment Failure; D005260:Female; D006801:Humans; D008297:Male; D018670:Monitoring, Ambulatory / Q000379:methods*; D008991:Monitoring, Physiologic / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D001786:Blood Glucose