Glucose control during hybrid closed loop using an enhanced vs standard algorithm in adults with type 1 diabetes in a supervised hotel setting

Participants will be assigned the Minimed Medtronic 670G system version 3.1 and the Minimed Medtronic 670G 3.0 closed loop systems in random order for a period of 7- days each, with stages separated by 1 week. The study is a two-stage randomized crossover study in a supervised live-in setting (hotel facility) performed in pump-experienced adults with type 1 diabetes. The MiniMed™ 670G system (Medtronic, Northridge, CA) includes the features of a conventional sensor augmented insulin pump, and also incorporates a PID control algorithm with the addition of insulin feedback plus limits on the maximum rate of insulin delivery and duration of insulin suspension. This control algorithm automatically determines the insulin dose based on information from the continuous glucose monitor (Enlite 3 sensor and GST3 Minilink transmitter) every 5 minutes, and calculates the insulin dose to maintain the individual within target glucose range. Based upon prior experience modifications have been made to the current iteration of the control algorithm (Version 3.0) resulting in Version 3.1 that aims to improve hyperglycaemia correction and time spent in automode. The system includes two external devices - an insulin pump and a continuous glucose monitor. The insulin pump can sit anywhere on the body and is connected to a subcutaneous cannula via plastic tubing (an infusion set). The cannula is generally inserted in the subcutaneous tissue on the abdomen or the buttock. The continuous glucose monitor is generally worn on the abdomen but can be worn anywhere there is an adequate amount of subcutaneous tissue. It sits on the skin above the inserted subcutaneous sensor. Participants will be required to perform at least 3 fingerpick glucose levels per day for sensor calibration using the Contour Next Link 2.4 blood glucose meter. Glucose data will be collected for each entire study week. Participants will also undergo 4 challenges to the closed loop system (each one performed on a separate day) , these including a missed bolus insulin dose (or unannounced meal), a high fat meal containing 40g of fat, a high GI meal (glycemic index ~70, glycemic load ~45) and a 40 minute bout of high intensity interval exercise (including five minutes of warm-up, then six repetitions of 4 minutes of exercise at high intensity (75% of age-predicted maximal heart rate) followed by 2 minutes of complete rest, an additional 4 minutes rest will be provided between the third and fourth repetitions). Data on intervention adherence defined as time in closed loop (automode) will be available via device upload and will be analysed. There will be no specific strategies used to maintain or improve fidelity other than device training and education prior to the study weeks.