EFFECTIVE SITE OF BRONCHODILATION BY BETA-ADRENERGIC AND ANTICHOLINERGIC AGENTS IN PATIENTS WITH CHRONIC OBSTRUCTIVE PULMONARY-DISEASE - DIRECT MEASUREMENT OF INTRABRONCHIAL PRESSURE WITH A NEW CATHETER

To study the effective site of bronchodilators in patients with chronic obstructive pulmonary disease (COPD), a catheter tip micromanometer sensing lateral pressure of the airway was wedged into the right lower lobe of a bronchus, 3 mm inner diameter, in 14 patients with COPD. We simultaneously measured mouth flow, transpulmonary pressure (PL) and intra-airway lateral pressure during quiet tidal breathing. Total pulmonary resistance (RL) was calculated from PL and mouth flow, and central airway resistance (RC) was calculated from intra-airway lateral pressure and mouth flow Peripheral airway resistance (RP) was obtained by the subtraction of RC from RL. This technique permitted identification of the site of changes in airway resistance. Atropine sulfate (5 mg/ml) was continuously inhaled during tidal breathing for 1 min by seven patients (Group A), and the other seven patients (Group B) Inhaled fenoterol (1 mg/ml) for 1 min. The doses that were actually delivered were 0.75 mg for atropine sulfate and 0.15 mg for fenoterol. The baseline resistances of RC and RP were 3.9 +/- 0.8 and 3.7 +/- 0.6 cm H2O/L/s in Group A, and 4.3 +/- 0.5 and 3.5 +/-0.4 cm H2O/L/s in Group B, respectively. Both atropine sulfate and fenoterol significantly decreased RL by an average of 2.4 and 2.6 cm H2O/L/s, and there was no significant difference between them (p < 0.20). The percentage decrease in resistance from the baseline values by fenoterol did not differ significantly between RC and RP (p > 0.20). However, atropine sulfate significantly decreased RC more than RP. These results suggest that aerosols of anticholinergic agents act predominantly on the central airways and that those of beta-adrenergic agents dilate both the central and the peripheral airways in patients with COPD.