Imaging sites of airway obstruction and measuring functional responses to bronchodilator treatment in asthma.

The sites of airway obstruction and dilatation after terbutaline administration were studied by inhalation imaging and pulmonary function tests in 12 stable asthmatic patients. Inhaled terbutaline as a therapeutic aerosol decreased airway resistance (Raw) and improved radioaerosol (Ae) images in nine, delta V max50 in three, and xenon (Xe) images in five of 12 subjects, suggesting that its predominant site of action was on major airways. Subcutaneously injected terbutaline improved Raw, delta V max50, and Ae images in 11 and Xe images in eight subjects indicating that it released bronchospasm in the major and minor airways. These findings in asthma suggest that aerosol and Xe imaging procedures are sensitive indicators of large and small airway obstruction respectively.