Maximal expiratory flow rates and airway resistance following histamine aerosols in asthmatics

Lung volumes, maximal expiratory flow rates (MEFR) and airway resistance were measured with a pressure corrected flow plethysmography in 13 asymptomatic asthmatics, before and after an induced bronchospasm with histamine aerosols. During bronchoconstriction all indices, except total lung capacity, changed significantly from control values. Specific airway conductance (SGaw) decreased on average by 49%, while MEF at 50 and 25% control vital capacity decreased by 44 and 56%, respectively. In 5 patients, at low concentrations of histamine, there was a discrepancy between changes in MEFR and SGaw: in 3 MEFR did not change while SGaw decreased, and in 2 others there was no change in SGaw but a substantial decrease of MEFR. At increased concentration of histamine both indices decreased together. It is concluded that MEFR and SGaw have a comparable merit to reflect a moderate or severe bronchoconstriction. Both indices, however, have to be measured when only a minor bronchospasm is produced, in order to avoid a false negative result.SCOPUS: ar.j