Introduction: Lung disease in cystic fibrosis (CF) begins early in life but the capabilities for detecting abnormalities of pulmonary dysfunction in children remain limited.
Objective: The study aimed to evaluate the early progression of lung function by the analysis of pulmonary hyperinflation, ventilation inhomogeneity (VI), trapped gas and airway obstruction with age.
Methods: One hundred CF children aged 7 to 18, divided into two groups aged 7 to 12 (n = 40) and 13 to 18 (n = 60), were enrolled. Patients performed multiple-breath nitrogen washout (MBNW) tests and plethysmography for measurements of lung clearance index (LCI), functional residual capacity (FRCpleth , FRCMBNW ), volume of trapped gas (VT ), total resistance, and effective and specific effective airway resistance (Reff , sReff ).
Results: We obtained a positive correlation of FRCpleth , FRCMBNW , and LCI with age. A linear correlation between FRCMBNW and FRCpleth (P < .0001) was observed. VI was higher in the group of older patients (9.79 in the group aged 7-12 and 11.67 in the group aged 13-18). An increased effective specific airway resistance >2 (z-score) was present in 58% of all subjects (50% and 63.3%, respectively). Pulmonary hyperinflation (FRCpleth >2 z-score) was observed in 33% of all patients: 25% and 36.6%, respectively. Trapped gas (VT > 2 z-score) was present in 18% of all children: 30% and 10%, respectively.
Conclusion: A gradual decline in lung function is associated with an increase in VI, airway obstruction, pulmonary hyperinflation and development of trapped gas. In children who cannot perform either spirometry or plethysmography, MBNW can deliver a measurement of LCI connecting with VI as well as FRCMBNW to indicate indirectly the increase of hyperinflation.
Keywords: cystic fibrosis; functional residual capacity; lung clearance index; pulmonary function testing; ventilation inhomogeneity.
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