Background: Hybrid closed loop (HCL) insulin delivery with the Medtronic MiniMed 670G system is safe and effective in improving glycemia for people with type 1 diabetes (T1D). Aims: To compare glucose control, CL exits and alarm frequency with standard HCL vs. enhanced HCL (eHCL) systems. Methods: Pump experienced adults with T1D (n=11; 9 women; mean[SD] age: 51[15]Y; HbA1c 7.5[1.0]%) were assigned in random order HCL and eHCL for 1 week each in a supervised live-in setting. eHCL incorporated enhanced bolus reminders and iterative changes broadening glucose and insulin delivery parameters permitting persistence in CL. For both HCL and eHCL insulin delivery was by a Medtronic pump with identical interventions (missed bolus, exercise, high GI and high fat meals), insulin action times and insulin-carbohydrate ratios implemented. The primary outcome was CGM time in target range. Results: eHCL resulted in fewer CL alerts and exits. Time in target and mean glucose favored eHCL but did not reach significance (Table). No episodes of severe hypoglycemia or ketoacidosis occurred. Conclusions: Iterative changes to the Medtronic HCL system resulted in trends towards improved glycemia, fewer CL exits and alerts without compromising safety, despite multiple food and exercise challenges during the study periods. Longer term studies at home are required to confirm these findings. Table: All results are Mean (SD); *NS= Not Significant.HCL (n=11)eHCL (n=11)pInsulin DeliveryTotal daily insulin (units/day)44 (18)47 (24)NS*Daily basal (%)55 (8)55 (7)NS*Daily bolus (%)45 (8)45 (7)NS*Daily insulin to carbohydrate ratio9.6 (3.1)9.6 (3.1)NS*Insulin action time (hrs)3.7 (0.6)3.7 (0.6)NS*Glucose Metrics% time in 70-180mg/dL69 (11)74 (10)0.16Mean sensor glucose (mg/dL)160 (13)151 (11)0.091Time <70mg/dL (%)1.9 (2.4)1.2 (1.2)0.42Time <50mg/dL (%)0.4 (0.5)0.2 (0.3)0.21Time>180mg/dL (%)29 (11)24 (9)0.37Time >250mg/dL (%)7.3 (5.6)6.1 (4.7)0.48Algorithm related Alerts and Dropout Alerts (n/week)8.6 (5.8)3.9 (2.8)0.01CL exits (n/week)3.5 (3.1)0 (0)0.004 Disclosure B. Paldus: None. M.H. Lee: None. H. Jones: None. S.A. McAuley: Research Support; Self; JDRF. Speaker's Bureau; Self; Novo Nordisk Inc., Australian Diabetes Society. J.C. Horsburgh: None. K.L. Roem: None. G. Ward: None. R. MacIsaac: None. N. Cohen: None. P.G. Colman: None. A. Jenkins: Research Support; Self; Medtronic, Mylan, Sanofi-Aventis. D.N. O'Neal: Research Support; Self; Medtronic MiniMed, Inc.. Advisory Panel; Self; Medtronic MiniMed, Inc.. Speaker's Bureau; Self; Medtronic MiniMed, Inc.. Advisory Panel; Self; Abbott. Speaker's Bureau; Self; Novo Nordisk Inc.. Advisory Panel; Self; Novo Nordisk Inc.. Research Support; Self; Novo Nordisk Inc.. Advisory Panel; Self; Sanofi. Research Support; Self; Sanofi.

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Sybil McAuley

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