Objective and background: The addition of an alternative class of long-acting bronchodilator is recommended for COPD patients who do not respond satisfactorily to monotherapy. The aim of this study was to investigate the additive benefit of tiotropium in severe COPD and to establish whether the improvement in lung function in these patients can be predicted from their acute bronchodilator response to ipratropium or salbutamol.
Methodology: Forty-six patients with severe COPD treated with inhaled long-acting beta(2) agonists and corticosteroids (LABA/CS) were enrolled. Their prebronchodilator FEV(1) was less than 50% of the predicted value. Tiotropium (18 microg, once daily) was added via a dry-powder inhaler device. After a month of treatment, tiotropium was stopped but their previous medication was continued. Patients were reassessed a month later. Acute bronchodilator response to ipratropium and salbutamol was assessed prior to tiotropium treatment. Pulmonary function and health status were evaluated.
Results: Adding tiotropium significantly improved FVC, FEV(1) and inspiratory capacity (IC). The increase in FVC was significantly associated with an increase in IC (r = 0.36, P = 0.019) and a decrease in residual volume (r =-0.56, P < 0.001). Total scores of St. George Respiratory Questionnaire scores were significantly improved after adding tiotropium treatment (P < 0.001). After tiotropium withdrawal, FVC, FEV(1) and IC decreased markedly. Bronchodilator response to ipratropium did not predict the tiotropium-mediated improvement in FEV(1) or FVC.
Conclusions: Adding tiotropium to inhaled LABA/CS can yield clinical benefits in lung function and improved quality of life in COPD patients, as both drugs act through separate yet complementary pathways to maintain airway calibre.