Continuous glucose monitoring indices predict poor FEV₁ recovery following cystic fibrosis pulmonary exacerbations

Background: Little is known about the effect of dysglycemia during cystic fibrosis pulmonary exacerbation (PEx) on recovery of FEV₁ percentage predicted (ppFEV₁) Methods: Continuous glucose monitoring (CGM) was commenced at the time of admission to hospital for PEx and continued for 6 weeks. The CGM indices, percentage of time glucose greater than 7.8 mmol/L (%T>7.8) and mean glucose were evaluated as predictors of absolute ppFEV₁ change following treatment of PEx. Results: Of the 20 participants who completed the study 13 (65%) had cystic fibrosis related diabetes (CFRD). The mean of both CGM indices were highest during the first week of pulmonary exacerbation and continued to decline over the first 4 weeks at which point they plateaued. Using multivariate regression models, factors which were predictive of maximum attained ppFEV₁ change over 6 weeks were %T>7.8, mean glucose, HbA1c and preadmission ppFEV₁ change from baseline. These relationships were independent of a diagnosis of CFRD, which was not associated with ppFEV₁ recovery. In a longitudinal model of ppFEV₁ change at weeks 1,2 and 6, the CGM index %T>7.8 approached significance as a predictive variable. Conclusions: Hyperglycemia during PEx in adult CF patients is associated with poorer ppFEV₁ recovery. Conversely, there was no association observed between CFRD diagnosis and ppFEV₁ improvement, suggesting that optimization of glycemic control in CFRD patients may positively influence recovery of lung function. Further clinical trials are required to evaluate the merits of intensive glycemic control in CFRD during PEx.