Additive efficacy of short-acting bronchodilators on dynamic hyperinflation and exercise tolerance in stable COPD patients treated with long-acting bronchodilators.

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.