Multivariable Artificial Pancreas for Various Exercise Types and Intensities

Abstract

Background: Exercise challenges people with type 1 diabetes in controlling their glucose concentration (GC). A multivariable adaptive artificial pancreas (MAAP) may lessen the burden.

Methods: The MAAP operates without any user input and computes insulin based on continuous glucose monitor and physical activity signals. To analyze performance, 18 60-h closed-loop experiments with 96 exercise sessions with three different protocols were completed. Each day, the subjects completed one resistance and one treadmill exercise (moderate continuous training [MCT] or high-intensity interval training [HIIT]). The primary outcome is time spent in each glycemic range during the exercise + recovery period. Secondary measures include average GC and average change in GC during each exercise modality.

Results: The GC during exercise + recovery periods were within the euglycemic range (70-180 mg/dL) for 69.9% of the time and within a safe glycemic range for exercise (70-250 mg/dL) for 93.0% of the time. The exercise sessions are defined to begin 30 min before the start of exercise and end 2 h after start of exercise. The GC were within the severe hypoglycemia (<55 mg/dL), moderate hypoglycemia (55-70 mg/dL), moderate hyperglycemia (180-250 mg/dL), and severe hyperglycemia (>250 mg/dL) for 0.9%, 1.3%, 23.1%, and 4.8% of the time, respectively. The average GC decline during exercise differed with exercise type (P = 0.0097) with a significant difference between the MCT and resistance (P = 0.0075). To prevent large GC decreases leading to hypoglycemia, MAAP recommended carbohydrates in 59% of MCT, 50% of HIIT, and 39% of resistance sessions.

Conclusions: A consistent GC decline occurred in exercise and recovery periods, which differed with exercise type. The average GC at the start of exercise was above target (185.5 ± 56.6 mg/dL for MCT, 166.9 ± 61.9 mg/dL for resistance training, and 171.7 ± 41.4 mg/dL HIIT), making a small decrease desirable. Hypoglycemic events occurred in 14.6% of exercise sessions and represented only 2.22% of the exercise and recovery period.

Keywords: Artificial pancreas; Exercise; Type 1 diabetes..

Conflict of interest statement

No competing financial interests exist.

Figures

FIG. 1.

The exercise type and frequency protocol.

FIG. 2.

Glucose traces (mean and standard deviation) during MCT, RT, and HIIT exercises. The solid black line represents the mean of CGM, and the shaded gray region represents one standard deviation of CGM for all experiments. Dotted lines indicate hypoglycemia (70 mg/dL) and hyperglycemia (180 mg/dL). CGM, continuous glucose monitor; HIIT, high-intensity interval training; MCT, moderate continuous training; RT, resistance training.

FIG. 3.

Visual representation of MAAP performance in one experiment. MAAP, multivariable adaptive artificial pancreas.