Lung function in children with hypersensitivity pneumonitis.

Pulmonary function tests were performed on 12 children with hypersensitivity pneumonitis (HP) aged from 4-15 years (10 with bird breeder's lung and 2 with farmer's lung). Lung volumes, lung mechanics (lung resistance, dynamic lung compliance (CLdyn], lung transfer factor for CO (TLCO), and blood gases were measured. Eleven children ceased to be exposed to the antigen, and the functional course was studied as a function of time after the cessation of exposure (CE). During the short term (less than 2 months after CE) initial hypoxemia was observed and CLdyn and TLCO were below normal. Two months after CE, blood gases were normal in most of the cases. A persistent hypoxemia appeared to be an unfavorable prognostic factor. CLdyn was normal by the eighth month after CE, while TLCO improved more slowly and remained significantly decreased in one case. In our series the children under 10 years had less functional abnormalities and normalized more rapidly than the older children. The one child without CE, had major functional abnormalities.