Abstract
Introduction: Ventilation heterogeneity (VH) is an early finding in cystic fibrosis (CF) lung disease. Scond, derived from phase III slope analysis of multiple-breath washout (MBW), is believed to reflect convection-dependent VH. Hyperpolarised gas MRI (HP-MRI) is sensitive to regional VH & may help elucidate the mechanisms underlying Scond.
Aim: To assess the relationship between Scond & VH indices from HP-MRI in children with mild CF & healthy controls (HC).
Methods: 19 children with CF & 10 HC completed spirometry, supine MBW & HP-MRI. HP-MRI was quantified using coefficient of variance of lung signal intensity (CV) & unventilated defect volume (VD).
Results: All subjects had FEV1 z-score>-1.96. Compared to HC, CF subjects had significantly higher (p<0.05) mean LCI(7.7 vs 6.6), Scond(0.054 vs 0.025), CV(13.5 vs 12.3%) & VD(2.3 vs 1.5%) though no significant difference in FEV1 or Sacin. There were strong correlations between Scond & both CV (r=0.75, p<0.01 Figure 1) & VD (r=0.65, p<0.01). Correlations between LCI & HP-MRI were weaker. FEV1 did not correlate with VH parameters.
Conclusion: In mild CF, VH from supine MBW & HP-MRI is raised in comparison to HC. Scond demonstrates a strong relationship with CV & VD and appears to be the MBW metric most closely associated with VH seen on MRI in early CF lung disease. These findings could help shed light on the contribution of regional lung VH to the Scond signal.
- Copyright ©the authors 2016