In patients with
COPD, a relationship between
breathlessness and respiratory effort, assessed in terms of mouth occlusion pressure (P0.1), has been described. To evaluate the short-term effects of inhaled
terbutaline on
breathlessness, breathing pattern, and P0.1 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 micrograms inhaled
terbutaline or placebo.
Breathlessness, using the Borg scale, breathing pattern, and P0.1 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 P0.1 (0.31 +/- 0.07 vs 0.21 +/- 0.05 kPa; p < 0.001) after
terbutaline inhalation was observed. Borg score was correlated with P0.1 in all patients. Moreover, changes in Borg score after medication were directly proportional to P0.1 changes (r = 0.85; p < 0.01). We conclude that
terbutaline decreases central inspiratory drive and improves
breathlessness in patients with nonreversible
COPD.