The purpose of this study was to clarify the additive efficacy of short-acting β(2)-agonists (
SABA) or
muscarinic antagonists (SAMA) on dynamic hyperinflation and exercise tolerance in patients with
chronic obstructive pulmonary disease (
COPD) who had been treated with long-acting
bronchodilators. Thirty-two patients with stable
COPD who had been treated with long-acting
bronchodilators, including long-acting
muscarinic antagonists (LAMA), were examined by pulmonary function tests, dynamic hyperinflation evaluated by the method of step-wise metronome-paced incremental
hyperventilation, and the incremental shuttle walking test before and after inhalation of
SABA or SAMA. The additive efficacy of the two drugs was analyzed. Inhalation of
SABA and SAMA improved airflow limitation and dynamic hyperinflation in stable
COPD patients who had been treated with LAMA. Inhalation of
SABA decreased respiratory resistance and the difference in respiratory resistance at 5 Hz and 20 Hz. On the whole, the additive efficacy of
SABA on airflow limitation and dynamic hyperinflation was superior to that of SAMA. Furthermore, inhalation of
SABA resulted in relief of
breathlessness during exercise and significant improvement in exercise capacity. Inhalation of
SABA resulted in significant improvement in exercise tolerance, which may have been due to improvement in dynamic hyperinflation. Single use of
SABA before exercise, in addition to regular treatment with LAMA, may therefore be useful in stable
COPD patients.