The Effect of the Closed-Loop Control System on Blood Glucose Control With Exercise: A Critically Appraised Topic

Context: Exercise can cause fluctuations in blood glucose control in type 1 diabetics. For athletes with type 1 diabetes, maintenance of blood glucose within an ideal range may be difficult. Objective: To determine, in individuals with type 1 diabetes, the effectiveness of the closed loop control system versus the open loop control system in keeping blood glucose levels in the ideal range with exercise. Data Sources: A search of PubMed was conducted in June of 2020 using the Boolean phrases: (closed loop control system OR artificial pancreas) AND type 1 diabetes AND exercise AND ideal range AND adolescents, artificial pancreas AND glucose prediction AND exercise. Study Selection: Titles were reviewed for relevance, the abstract was then assessed for applicability, and finally the full text was examined. Articles were included that examined the percent of time in the ideal blood glucose range when exercise occurred during that day. Articles were excluded that didn't compare the closed loop and open loop control systems and articles that did not involve exercise. Data Extraction: The PEDro scale was used to determine the methodological quality of the included studies. The measure addressed was the percent of time in the ideal blood glucose range of 70-180 mg/dL. 95% Confidence Intervals and Cohen's D were calculated for each article. Data Synthesis: The search yielded 268 articles and 3 were selected for inclusion. The two randomized controlled trials scored 9/10 on the PEDro scale and the randomized two-arm crossover clinical trial scored 9/10 on the PEDro scale. Percent time spent in the ideal blood glucose range when exercise was performed was significantly higher in the closed loop group versus the open loop group in each of the three studies. In one randomized control trial, mean time in the ideal range was 71.3% (SD = 17.6, 95% CI = 62.5, 80.10) in the closed loop group versus 64.7% (SD = 13.3, 95% CI = 58.1-71.4) in the open loop group. Cohen's D was 0.4. In the second randomized control trial, mean time in the ideal range was 73.5% (SD = 8.4, 95% CI = 70.1, 76.9) for the closed loop group versus 50% (SD = 26.8, 95% CI = 39.1, 60.9). Cohen's D was 1.2. The two-arm crossover clinical trial resulted in a mean time in target range of 84.1% (SD = 11.5, 95% CI = 79.0, 89.2) in the closed loop group versus 68.7% (SD = 13.9, 95% CI = 62.5, 74.9) in the open loop group. Cohen's D was 1.2. Conclusions: For adolescents with type 1 diabetes who exercise, the closed loop control system maintains blood glucose levels in the ideal range for a longer percent of time versus an open loop system. Each patient should be evaluated on a case-by-case basis with his/her healthcare team. Future research should examine the closed loop control system on specific energy systems.