Background. The use of insulin pumps is becoming a popular technique for insulin delivery among patients with type 1 diabetes mellitus (T1DM), but there is no consensus regarding the guidelines for proper pump use during exercise.Objective. To investigate the physiologic responses and risk of hypoglycemia among children and adolescents with T1DM when exercising with the pump on (PO) (50% of the basal rate) or pump off (PF).Methods. Ten subjects with T1DM (6 female subjects and 4 male subjects), 10 to 19 years of age, performed prolonged exercise (40–45 minutes) on a cycle ergometer ～2 hours after a standard breakfast and an insulin (Lispro) bolus. Complex carbohydrates (20 g) were provided before and after the exercise. Each patient exercised once with PO and once with PF, in a randomized, crossover (single-blind) manner. During exercise and 45 minutes of recovery, subjects were monitored for cardiorespiratory, metabolic, and hormonal responses. Blood glucose concentrations were recorded for 24 hours after exercise, with a continuous glucose monitoring system, to document late hypoglycemic events.Results. During exercise, blood glucose concentrations decreased by 59 ± 58 mg/dL (mean ± SD: 29 ± 24%) with PF and by 74 ± 51 mg/dL (35.5 ± 18%) with PO (not significant). No significant differences were found in cortisol, growth hormone, or noradrenaline levels between PO and PF. There were no differences in cardiorespiratory parameters, blood lactate concentrations, or free fatty acids concentrations between pump modes. Hypoglycemic events during exercise were asymptomatic and occurred for 2 subjects with PO and 2 with PF. Nine subjects had late hypoglycemia after PO, compared with 6 after PF (not significant).Conclusions. We found no advantage for subjects with either PO or PF during exercise, and we noted that late hypoglycemia was more common than hypoglycemia during exercise. However, PO was associated with a trend of increased risk for late hypoglycemia. We recommend that the pump be removed or turned off during prolonged exercise and that blood glucose concentrations be monitored for several hours after exercise, regardless of the pump mode.
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