Jm. Pinogarcia et al., SHORT-TERM EFFECTS OF INHALED BETA-ADRENERGIC AGONIST ON BREATHLESSNESS AND CENTRAL INSPIRATORY DRIVE IN PATIENTS WITH NONREVERSIBLE COPD, Chest, 110(3), 1996, pp. 637-641
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.