The implications of dysglycaemia on aerobic exercise and ventilatory function in cystic fibrosis

Background The development of cystic fibrosis (CF)-related diabetes (CFRD) in paediatric groups is associated with a reduced aerobic fitness. However, this has yet to be investigated in adults with more severe lung disease. Methods Cardiopulmonary exercise and glycaemic control tests were retrospectively analysed in 46 adults with CF (age: 26.9 y [range: 16.3–66.5 y]; forced expiratory volume in 1s: 65.3% [range: 26.8–105.7%]; 26 males), diagnosed with CFRD (n = 19), impaired glucose tolerance (IGT; n = 8) or normal glucose tolerance (NGT; n = 19). Results Maximal oxygen uptake (V˙O2max) was reduced in adults with IGT and CFRD compared to their age- and gender-matched counterparts with NGT (p < 0.05); however, there was no difference when lung function was included as a covariate (all p > 0.05). V˙O2max was greater in adults who experienced post-reactive hypoglycaemia vs. NGT without hypoglycaemia (p < 0.05). The frequency of ventilatory limitation (84%, 63% and 37%, respectively; p < 0.05) but not ventilation-perfusion mismatch (42%, 38% and 16%, respectively; p > 0.05), was greater with CFRD and IGT vs. NGT. There was also no difference in arterial oxygen saturation changes between groups (p > 0.05). Gender and body mass index were significant predictors of V˙O2max (adjusted R2 = 0.37, p < 0.01), but glycaemic control did not explain additional variance (p > 0.05). Conclusions Adults with CF-related dysglycaemia had a reduced V˙O2max compared to age- and gender-matched counterparts, due to a greater degree of CF lung disease in these populations.