Pulmonary function in severe chronic asthma in children during apparent clinical remission.

We have studied PEF, MEFV curves and the response to breathing He/O2 in 10 children (mean age 12 years) with severe steroid dependent asthma during a two year period. Abnormalities of ventilatory function were almost invariably present, with FEV1 and V50, breathing air or He/O2, the commonest indices of abnormality. FEV1 was comparable in sensitivity to V50 in detecting airflow obstruction. Clinical criteria of severity greatly underestimated the degree of functional impairment. The absolute, but not the relative response to inhalation of He/O2 was reduced at 50% VC and 25% VC. Following the inhalation of salbutamol, FEV1 V50 and V25 increased significantly in every case.