SHORT-TERM EFFECTS OF INHALED BETA-ADRENERGIC AGONIST ON BREATHLESSNESS AND CENTRAL INSPIRATORY DRIVE IN PATIENTS WITH NONREVERSIBLE COPD

In patients with COPD, a relationship between breathlessness and respi ratory effort, assessed in terms of mouth occlusion pressure (P-0.1), has been described. To evaluate the short-term effects of inhaled terb utaline on breathlessness, breathing pattern, and P-0.1 in patients wi th nonreversible COPD, we designed a randomized, double-blind, paralle l, placebo-controlled study. Twenty-five patients with stable nonrever sible COPD, mean age 64+/-11 years, were enrolled in the study. Patien ts received 500 mu g inhaled terbutaline or placebo. Breathlessness, u sing the Borg scale, breathing pattern, and P-0.1 were measured at bas eline and 30 min after inhalation. Terbutaline resulted in a significa nt decrease in Borg scale, while no differences were observed after pl acebo. No significant changes in breathing pattern were found. Neverth eless, a decrease in P-0.1 (0.31+/-0.07 vs 0.21+/-0.05 kPa; p<0.001) a fter terbutaline inhalation was observed. Borg score was correlated wi th P-0.1 in all patients. Moreover, changes in Borg score after medica tion were directly proportional to P-0.1 changes (r=0.85; p<0.01). We conclude that terbutaline decreases central inspiratory drive and impr oves breathlessness in patients with nonreversible COPD.