Hypoglycemia Prevention and User Acceptance of an Insulin Pump System with Predictive Low Glucose Management

Abstract

Background: The MiniMed 640G sensor-augmented insulin pump system (Medtronic, Inc., Northridge, CA) can automatically suspend insulin delivery in advance of predicted hypoglycemia and restart it upon recovery. The aims of this analysis were to determine the rate at which predicted hypoglycemia was avoided with this strategy, as well as to assess user acceptance of the system and its insulin management features.

Subjects and methods: Forty subjects with type 1 diabetes used the system for 4 weeks. We retrospectively evaluated performance of the system, using downloaded pump and sensor data, and evaluated user acceptance via questionnaires.

Results: There were 2,322 suspend before low events (2.1 per subject-day). The mean (± SD) duration of pump suspension events was 56.4 ± 9.6 min, and the mean subsequent sensor glucose (SG) nadir was 71.8 ± 5.2 mg/dL. SG values following 1,930 (83.1%) of the predictive suspensions did not reach the preset low limit. Nadir SG values of ≤50 and ≤60 mg/dL were seen in 207 (8.9%) and 356 (15.3%) of the predictive suspensions, respectively. Blood glucose (BG) and SG values before and during the study were comparable (P > 0.05). The mean absolute relative difference between paired SG and BG values was 10.9 ± 13.8%. Subjects felt confident using the system, agreed that it helped protect them from hypoglycemia, and wished to continue using it.

Conclusions: Automatic insulin pump suspension as implemented in the MiniMed 640G system can help patients avoid hypoglycemia, without significantly increasing hyperglycemia.

FIG. 1.

(A) Mean and SD of sensor glucose trajectories throughout suspend before low events lasting <30, 30 to <90, and ≥90 min. The line at 54 mg/dL (3.0 mmol/L) represents the most commonly used threshold value. (B) Number and proportion of nadir sensor glucose values following suspend before low events that were greater than the preset low limit (white) or were at or below the preset low limit (black).