The response of asthmatic patients and normal subjects to maximum respiratory manoeuvres. Spirometry--induced bronchoconstriction.

Fourteen atopic asthmatics, 12 non-atopic asthmatics, and 14 normal subjects performed a series of pairs of FEV1.0 measurements, with the first and second measurements separated by initially 10 seconds, then 30 seconds and finally 60 seconds. Two further pairs of FEV1.0 measurements were made at the interval that had produced the greatest fall in FEV1.0 to examine the consistency of this response. A correlation with bronchial lability on exercise testing was sought in 16 patients. In the asthmatics a further pair of FEV1.0 measurements was performed after bronchodilatation with 200 mcg salbutamol. Both atopic and non-atopic asthmatics showed a slight fall in FEV1.0 in successive measurements which was not seen in normal subjects. The small size of the fall is unlikely to interfere with spirometry results in clinical testing. Some subjects show a larger response and should be excluded from trials of drugs. Salbutamol diminished or abolished the response. The fall in FEV1.0 did not correlate with the results of exercise testing.