Is Lung Clearance Index (LCI) Affected by the Severity of Lung Disease in CF?

Background: LCI has been proven an effective tool in the detection of lung disease in CF. Objectives: a) To assess the correlation of ventilation inhomogeneity indices with structural damages of the lung, among different groups of disease severity and b) To compare the associations among MBW parameters with spirometry and CT. Method: Forty-four children and adolescents with CF participated in the study. Spirometry and multiple breath washout tests were performed. All children had a HRCT scan. The study population was divided into two groups, according to FEV1% predicted values: Group A: ≥ 85% predicted (normal) and Group B: 40-84% predicted (mild-moderate disease). Results: The patients’ mean age was 12.9 (5.67; 23.25) years, mean FEV1: 91.22 ± 24.22% and mean LCI: 10.72 ± 3.51. Children of Group A had significantly lower LCI, compared to Group B (p<0.001). Among the whole study group all the ventilation inhomogeneity indices were correlated with FVC%, FEV1% and FEF50% and the severity and extent of bronchiectasis, the generation of bronchial division and the presence of emphysema (p<0.05). Among patients with normal FEV1, MBW parameters showed stronger correlation with the structural changes of HRCT, while among patients with mild-moderate lung disease, they showed stronger correlation with spirometry. Conclusion: MBW is a reliable method to assess the structural and functional lung disease in CF. However in mild disease ventilation inhomogeneity outcomes were better associated with CT changes, while in mild moderate disease MBW outcomes were better associated with spirometry.