Emphysema with minor airway obstruction and abnormal tests of small airway disease.

In 9 patients complaining primarily of exertional dyspnea, the diagnosis of early emphysema was made on the basis of a decrease of the elastic recoil of the lung and of the single breath diffusing capacity, in the presence of only minor airway obstruction as estimated from the routine pulmonary function tests. Closing volume, the alveolar plateau, dynamic compliance and maximal flow at 50% of the vital capacity were markedly abnormal; the maximal flow-static recoil pressure relationships suggest, however, that none of the patients suffered from small airway disease. We conclude that one should systematically consider early emphysema in the differential diagnosis of small airway disease.