A dual stable-isotope study of the effect of altitude and simulated flight on glucose metabolism in type 1 diabetes: A randomised cross-over study

The impact of atmospheric pressure changes on glucose metabolism encountered in aviation on people with type 1 diabetes is controversial. A dual-isotope study was performed in a hypobaric chamber to simulate pressure changes experienced on commercial flights. The fasting and postprandial glucose kinetics of individuals with type 1 diabetes were evaluated across simulated in-flight cabin pressures (550mmHg; experimental arm) and ground level (750mmHg; control arm). The impact of ambient pressure on glucose disposal (Rd), endogenous glucose production (EGP), meal glucose appearance (Ra), and insulin concentrations were evaluated. Six male participants, aged 20-61 years, with a median BMI of 26.6 kg/m² were studied. Baseline glucose Rd, EGP, and meal Ra were not affected by ambient pressure changes. Postprandial glucose Rd was higher in hypobaric conditions than ground, percent change in postprandial glucose concentration was lower but postprandial EGP and meal Ra were not affected. Insulin concentration between 120-180 min was higher in the hypobaric simulation. The observed increase in glucose Rd for individuals with type 1 diabetes on insulin pumps may be related to the hypoxia and pressure changes experienced during flight. Since glucose profiles were unaffected, there is no evidence that insulin pump therapy is a risk factor in flight.