medwireNews: Using a dual-hormone closed-loop insulin delivery system that detects when the wearer is doing exercise results in a low rate of exercise-induced hypoglycemia, show findings from a small randomized study.
In the trial, 20 physically active patients with type 1 diabetes tested three types of artificial pancreas system during exercise in a randomly assigned order: a dual- or single-hormone system that detected when participants were exercising, and a single-hormone system designed to predict hypoglycemia and suspend insulin delivery accordingly.
Each system was tested for 4 days, two of which were spent in the clinic for 12 hours and included a supervised treadmill exercise session. On the other 2 days, participants undertook their usual activities at home.
These systems were tested against participants’ usual care with an insulin pump (ie, not closed-loop). During this period, they pre-emptively adjusted their insulin dose when they planned to do exercise, achieving a low time in hypoglycemia during exercise, of 4.3%. The researchers say this “highlights the importance of patient education to prevent hypoglycemia,” adding that a “much needed” consensus statement on this issue has recently been published.
But “[t]he challenge is that patients often forget to make these adjustments or exercise is not scheduled in advance, which is why the development of automated systems is critical for patient safety and to reduce disease burden,” they note in Diabetes Care.
The dual-hormone (insulin plus glucagon) exercise-detection system gave the best result overall, at 3.4% of time in hypoglycemia, compared with 8.3% for the single-hormone exercise-detection system and 7.6% for the single-hormone system with insulin-suspend facility.
Jessica Castle and co-researchers from Oregon Health & Science University in Portland, USA, explain that the exercise-detection systems required users to confirm that they were exercising, after which insulin delivery was suspended for 30 minutes and then reinstated at half the typically provided rate for a further 60 minutes.
And in the dual-hormone system, exercise confirmation also resulted in the target glucose for glucagon being raised from 95 to 120 mg/dL and the maximum glucagon dose doubled. If the user developed hypoglycemia within 1.5 hours of starting exercise then the target glucose would be increased further on the next occasion, causing earlier delivery of glucagon.
There were drawbacks to the dual-hormone system, however. The researchers note the increased complexity and cost, and that five participants experienced nausea while using it, although so did three during the low-glucose-suspend period and one during the usual care period.
They add that an earlier exercise announcement or a pre-exercise snack (which was not allowed in the current study) may improve outcomes with the single-hormone systems, although this applies only to planned exercise.
“The safety of chronic glucagon delivery in humans needs to be established before commercialization of dual-hormone systems, and the dose of glucagon should be kept as low as possible,” the team concludes.
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