Abstract
Objective Patients with Type 1 Diabetes Mellitus (T1DM) exhibit impaired baroreflex sensitivity (BRS) which is worsened during hypoglycemia and can be improved with hyperoxia. These data support a contribution of hypoxia to impairments in BRS in T1DM. Given the prevalence of both nocturnal hypoglycemia and sleep disordered breathing in this population, we sought to examine the combined effect of hypoglycemia and hypoxia on BRS. We hypothesized the fall in BRS with hypoglycemia in patients with T1DM would be further reduced when combined with hypoxia. Methods Subjects with T1DM (n=13) completed two 180-minute hyperinsulinemic (2 mU/kg TBW/min), hypoglycemic (~3.3 µmol/mL) clamps separated by a minimum of 1 week and randomized to normoxia (SaO2 ~98%) or hypoxia (SaO2 ~85%). Heart rate (ECG) and blood pressure (finger photoplethysmography) were analyzed at baseline and during the hypoglycemic clamp for measures of spontaneous cardiac BRS (sCBRS). Results Hypoglycemia resulted in significant reductions in sCBRS when compared with baseline levels (Main effect of hypoglycemia: ms/mmHg, p=0.01; beat/min/mmHg, p=0.19). sCBRS was further impaired during hypoxia (Main effect of hypoxia: ms/mmHg, p=0.03; beat/min/mmHg, p=0.05). Conclusions Acute hypoxia worsens hypoglycemia-mediated impairments in BRS in patients with T1DM. These results highlight the potential cumulative dangers of hypoglycemia and hypoxia in this vulnerable population. Research Support: NIH DK090541, Dutch Heart Foundation
Published Version
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