Lung function deterioration in school children with cystic fibrosis.

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.