Possible site of bronchodilation due to inhaled procaterol aerosol in asthmatic patients

We studied the effective site of an inhaled aerosol of procaterol, a beta 2-selective adrenergic bronchodilator, in 8 asthmatic patients whose basal lung functions are almost within the normal range in both slow vital capacity (VC) and forced expiratory volume in one second (FEV1.0), and are free from asthmatic attack. In patients who had received procaterol 30 min after inhalation of aerosol, there was no significant change in VC, although FEV1.0, maximal expiratory flow at 50% VC (V50), maximal expiratory flow at 25% VC (V25) and maximal expiratory flow at 30% VC of partial maximal expiratory flow volume curve (V30p) improved significantly. On the other hand, in those who had received placebo, none of the parameters changed. Furthermore, R1 decreased and C0.5 increased significantly during the first 5 min after inhalation of procaterol aerosol. After an interval of 5 min, R1 did not change any further, while C0.5 continued to improve until 30 min after inhalation of procaterol. These results suggest that procaterol may first dilate the large airway and then may gradually dilate the small airway in bronchial asthma.