Short-term Effects of Inhaled β-Adrenergic Agonist on Breathlessness and Central Inspiratory Drive in Patients With Nonreversible COPD

In patients with COPD, a relationship between breathlessness and respiratory effort, assessed in terms of mouth occlusion pressure (P 0.1 ), has been described. To evaluate the short-term effects of inhaled terbutaline on breathlessness, breathing pattern, and P 0.1 in patients with nonreversible COPD, we designed a randomized, double-blind, parallel, placebo-controlled study. Twenty-five patients with stable nonreversible COPD, mean age 64±11 years, were enrolled in the study. Patients received 500 µg inhaled terbutaline or placebo. Breathlessness, using the Borg scale, breathing pattern, and P 0.1 were measured at baseline and 30 min after inhalation. Terbutaline resulted in a significant decrease in Borg scale, while no differences were observed after placebo. No significant changes in breathing pattern were found. Nevertheless, a decrease in P 0.1 (0.31±0.07 vs 0.21±0.05 kPa; p