Box 1.

The Closed-Loop System Used During the Trial

The CamAPS FX system combines real-time CGM (CGM), the Dexcom G6 CGM sensor and transmitter (Dexcom, San Diego, CA) with an insulin pump, the DANA RS (Sooil, Seoul, South Korea), via the Cambridge model predictive control algorithm (CamDiab, Cambridge, UK), hosted on an unlocked Android smartphone (Galaxy S7–S10, Samsung, South Korea), running Android 8 OS or above.

The smartphone/app communicates wirelessly with the CGM sensor and insulin pump, subject to being kept within 5–10 meters range of both devices. It uses CGM sensor data to direct (basal/background) insulin delivery via the pump, adjusting this automatically every 8–12 min. As well as being used to administer premeal bolus doses, the CamAPS FX app is used to (1) set personal glucose targets, typically 5.5 mmol/L (99 mg/dL) in early pregnancy and 5.0 mmol/L (90 mg/dL) after 14–16 weeks, consistent with achieving and maintaining pregnancy glucose targets; (2) adjust the rate of insulin delivery using ‘Boost’ and ‘Ease-off settings’; (3) personalize alarms to alert about high/low glucose levels; and (4) view ‘real-time’ glucose levels, rate of insulin delivery and summary statistics.

Remote monitoring capabilities

The app automatically uploads data to the cloud (Glooko/Diasend; Göteborg, Sweden), enabling data sharing with other individuals, including healthcare professionals and partners/family members. Using the CamAPS FX clinical portal, healthcare professionals at local sites and members of the trial team could access the following data:

• ‘Real-time’ and retrospective graphs displaying CGM and capillary blood glucose levels, rate of insulin delivery, insulin boluses, and carbohydrate intake, high/low glucose range, Boost and Ease-off status, and system status (operational or interrupted/switched off).

• Summary statistics (daily, weekly, monthly, or three-monthly periods), including mean CGM glucose, GMI or estimated HbA1c, time in/below/above target glucose range, number and average duration of hypos, total daily dose/bolus/basal insulin, and percentage of time in operation.

Healthcare professionals could also receive summary CamAPS FX reports by email, daily, weekly, or monthly, for participants using the HCL at their site. These included key glycemic metrics (mean glucose; time in/above/below target glucose range), insulin doses, and system metrics (HCL use, CGM use, and number of alarms issued during the day and at night).

CGM, continuous glucose monitor; GMI, Glucose Management Indicator; HbA1c, glycated hemoglobin; HCL, hybrid closed-loop.